Macrophage plasminogen activator: modulation of enzyme production by anti-inflammatory steroids, mitotic inhibitors, and cyclic nucleotides

Prostaglandin E2 and plasminogen activators in human milk and their secretion by milk macrophages

Human milk was shown to contain prostaglandin E2 (PGE2) and plasminogen activator (PA) at variable concentrations depending on the time of lactation after delivery. Milk PA was functionally and immunologically identical to urokinase. A follow-up study showed that the maximum PGE2 concentrations occurred during the second week while the maximum PA concentration was observed at the end of the first week of lactation. Milk macrophages cultured in vitro were able to secrete both PGE2 and PA. When cells were activated by concanavalin A (ConA) or E. coli lipopolysaccharide (LPS), PGE2 secretion increased dramatically while PA secretion did not. The ability of activated macrophages to secrete PGE2 was at its highest shortly after delivery. It then progressively decreased during lactation. The possible physiological role of PGE2 and PA on the gastrointestinal tract of breast fed infants is discussed.

The stimulation of human synovial fibroblast plasminogen activator activity. Involvement of cyclic AMP and cyclooxygenase products

The plasminogen activator activity of human synovial fibroblasts is raised by a monocyte-derived polypeptide, synovial activator and also by all-trans retinoic acid. The elevation of the synovial cell plasminogen activator activity by the two stimuli is potentiated both by agents which can raise cellular cyclic AMP levels, namely prostaglandin E2, cholera toxin and 3-isobutyl-1-methylxanthine, and also by exogenous 8-bromocyclic AMP. These findings suggest that there might be a substrate, which is phosphorylated by a cyclic AMP-dependent protein kinase and which is important in the modulation of the synovial cell plasminogen activator activity by the two stimuli. Prostanoids can be important in the stimulation of the synovial fibroblast plasminogen activator activity by mononuclear cell supernatants, since indomethacin can inhibit the increase in proteinase activity.

Dexamethasone inhibits antitumor potential of activated macrophages by a receptor mediated action

The capacity to inhibit P815 mastocytoma growth was induced in macrophages elicited by trehalose dimycolate by a short in vitro treatment with 10 ng/ml LPS. Activation by LPS was associated with a 3 fold increase in the rate of glucose consumption by macrophages. Incubation of activated macrophages with the glucocorticoid dexamethasone (greater than or equal to 10(-8) M) for several hours (greater than or equal to 5 h) resulted in an inhibition of antitumoral activity and a decrease of glucose consumption. Hydrogen peroxide production is a property expressed by trehalose dimycolate-elicited macrophages independently of the presence of LPS. The capacity to release hydrogen peroxide upon triggering was not affected by a pretreatment of macrophages by dexamethasone. The antiglucocorticoid compound RU 38486, known to bind with a high affinity to glucocorticoid receptors without agonist effect, prevented the inhibitory actions of dexamethasone, indicating that these are receptor-mediated.

Cortisol at physiological concentrations and prostaglandin E2 are additive inhibitors of human natural killer cell activity

The effects of cortisol and prostaglandin E2 on preparations of human peripheral blood mononuclear cells that mediate natural killer cytotoxicity were evaluated. Natural killer cell activity was measured using 51Cr-labelled K562 target cells and effector to target cell (E:T) ratios of 50:1, 25:1, 12.5:1 and 6:1. In vitro preincubation of mononuclear cell preparations for 20 h with 1 X 10(-8) to 1 X 10(-5) M cortisol resulted in a significant decrease of natural killer cell activity. The magnitude of the suppression was directly related to the steroid concentration and inversely related to the E:T ratio. Exposure of cortisol-treated mononuclear cells to 1 X 10(-6) M prostaglandin E2 resulted in a significantly higher level of inhibition than after treatment with the two agents singularly. In contrast, the concomitant incubation with 1 X 10(-5) to 1 X 10(-4) M theophylline, or with 1 X 10(-6) to 1 X 10(-5) M isobutyl-methylxanthine, two widely used phosphodiesterase inhibitors, failed to demonstrate a significant enhancement of cortisol-induced suppression. Prostaglandin E2-dependent inhibition, on the other hand, was more intense after the inhibition of phosphodiesterase activity. Taken together, these results show that cortisol at physiological concentrations has the property of depressing human natural killer cell activity in vitro and suggest that endogenous glucocorticoids play a role in the in vivo regulation of this natural cytotoxicity. Additionally, cortisol and prostaglandin E2 are additive inhibitors of natural killer cell activity. Since the effect of cortisol in our experiments was not changed by theophylline or isobutyl-methylxanthine it is conceivable that the hormone acts at a level different from the adenylate cyclase/phosphodiesterase system.

Effect of prostaglandins on interferon synthesis in murine macrophage-like cell lines

Murine macrophage-like cell lines were used to determine whether exogenously added prostaglandins and endogenous prostaglandins suppress interferon (IFN) synthesis in macrophages. The amount of IFN produced by J774A.1 cells induced with bacterial lipopolysaccharide (LPS) was reduced by 0.1 and 1 microM PGE1 or PGE2. These prostaglandins also inhibited Newcastle disease virus (NDV) induced IFN production, but only at a concentration of 1 microM. Thromboxane B2 at 0.01 to 1 microM had no effect on IFN production. Cells treated before, during, or before and during IFN synthesis with 0.15 to 4.8 microM indomethacin to inhibit prostaglandin synthesis did not increase IFN yields. Indomethacin also had no effect on NDV-induced IFN production by P388D1 and PU5-1.8 cells, and these cells remained nonresponsive to LPS for IFN production. These results indicate that endogenous levels of cyclooxygenase-dependent metabolites of arachidonic acid do not regulate IFN synthesis in macrophages.

Transplantation of the B16-F10 melanoma to the anterior chamber of the eye uniquely fails to elicit elevation in plasma proteinase activity

Transplantation of B16-F10 melanoma cells to C57BL/6 mice led to increased levels of plasma proteinase activity in tumor-bearing mice if the tumor was transplanted to a subcutaneous site or intraperitoneally. However, transplantation of the tumor cells to the anterior chamber of the eye did not induce elevations in plasma proteinase activity. This latter result was observed when the tumor cells were transplanted to intact or splenectomized animals. These results indicate that tumors in the anterior chamber of the eye are perceived in a unique fashion by the host and that host systems, rather than the tumor, are responsible for the altered plasma proteinase activity observed in animals bearing the tumor at other sites. The failure of animals bearing intraocular tumors to develop elevated proteinase activation appeared to be a result of a failure of such tumors to impinge on specific host systems rather than the induction of a deviated host response.

Regulation of prostaglandin E2 and plasminogen activator by various immunomodulators in human monocytes

Mononuclear phagocyte populations and monocytes are able to produce, among numerous substances, a neutral protease, i.e. plasminogen activator (PA) and prostaglandins. Since it has been shown that prostaglandins (PGs) and particularly PGE2 could exert an inhibitory effect on PA production by macrophages, we have measured the in vitro production of PA and PGE2 by monocytes isolated from healthy donors. These monocytes were cultured either in the absence or the presence of various immunomodulators: lipopolysaccharide from E. coli, concanavalin A and RU 41740 or Biostim a broad spectrum immunostimulating agent isolated from Klebsiella pneumoniae (Cassenne Laboratories, France). The production of PGE2 was proportional to the number of monocytes per incubation, and at a given cell concentration varied greatly from one subject to another. When considering PGE2 productions, the type of the response to the different immunomodulators varied from subject to subject and ranged from stimulation to no effect, or even inhibition. Moreover, a statistically significant, inverse relationship exists between the spontaneous production of PGE2 and the effect of each immunomodulator. For a given subject, all agents always acted in the same way and there was an inverse relationship between the effects of the immunomodulators on plasminogen activator and PGE2 production.

Urokinase binding sites on human foreskin cells. Evidence for occupancy with endogenous urokinase

In cultures of human foreskin fibroblasts most of the cell surface binding sites for 2-chain urokinase are masked and can be exposed by 10 min. incubation on ice at pH 2.5 (A. Bajpai and J.B. Baker (1985), Biochem. Biophys. Res. Commun.133, 475-482). Here we show that incubation on ice at pH 2.5 also releases from the cell surface a plasminogen activator that is similar to 2-chain urokinase in terms of its electrophoretic mobility, chromatographic behavior on concanavalin A-Sepharose or p-amino-benzamidine-Sepharose, and sensitivity to anti-urokinase antibody. Two observations suggest that the masked binding sites are sites occupied by this cell surface urokinase. First, glucocorticoid-treated cells, which lack cell surface urokinase, have a large number of urokinase binding sites but none that are masked. Second, the extraction of surface urokinase and the exposure of urokinase binding sites exhibit similar pH dependence. Both are complete at about pH 4.0.

[Plasminogen activators: general aspects and recent developments]

Considerable interest in plasminogen activators as human thrombolytic drugs has stimulated rapid biotechnologic progresses. These enzymes have been classified in two immunochemically distinct groups: "urokinase-like" activators or u-PA which do not interact with fibrin and "tissue activator-like" activators or t-PA which interact with fibrin. Plasminogen activators are widely distributed in normal and malignant tissues and they are implicated in various physiological and pathological processes. They maintain the functional integrity of the vascular system and their presence may be of importance in tissue remodeling and cell migration. Urokinase and streptokinase are used in human thrombolytic therapy. However, the properties displayed by t-PA suggest that this enzyme may be a superior fibrinolytic agent. The primary structures of urokinase and t-PA are known; both enzymes have been synthesized by DNA technology. In order to produce t-PA in large quantities by gene cloning, intensive studies are conducted by pharmaceutical industries. Clinical trials using t-PA for dissolving thrombi in coronary heart disease, strokes and pulmonary embolism are in progress. This review presents the molecular and structural properties of plasminogen activators, as well as related physiological, pathological and therapeutic aspects.

Plasminogen activator in mouse and rat oocytes: induction during meiotic maturation

We have found that ovulated mouse and rat oocytes contain tissue-type plasminogen activator (PA). Primary oocytes isolated from ovaries did not contain the enzyme. During spontaneous meiotic maturation in vitro, tissue-type PA became detectable 5 hr after germinal vesicle breakdown. Induction of tissue-type PA activity was blocked by dibutyryl-cAMP or isobutylmethyl-xanthine as well as by cycloheximide, but not by actinomycin D or alpha-amanitin. These results suggest that tissue-type PA mRNA is present in primary oocytes, and that translation of this mRNA is triggered upon resumption of meiotic maturation. Tissue-type PA catalyzed proteolysis around live secondary oocytes and fertilized eggs, indicating secretion of the enzyme. Unlike secondary oocytes, fertilized eggs denuded of their zona pellucida no longer contained the enzyme, suggesting that tissue-type PA production stops at or around fertilization, and that the bulk of the enzyme is secreted at this time.

Macrophage-mediated modulation of hepatic function in multiple-system failure

Hepatic insufficiency associated with the multiple-system organ-failure (MSOF) syndrome is a frequent sequellae of sepsis and severe trauma. Although its etiology is poorly understood, there is a growing literature suggesting that it may be mediated in part by secretory products of cells of monocyte/macrophage lineage including Kupffer cells. Several investigators have reported in vitro macrophage/Kupffer cell-mediated cytotoxicity toward target cells following appropriate stimulation. In addition, in vivo hepatocyte toxicity has been documented following activation of the reticuloendothelial system. The role of several secretory products including active oxygen intermediates, neutral proteases, and interleukin 1 in this cell-mediated model of hepatocellular modulation is reviewed.

Opposing effects of dexamethasone on the clonal growth of granulocyte and macrophage progenitor cells and on the phagocytic capability of mononuclear phagocytes at different stages of differentiation

Dexamethasone, a synthetic glucocorticosteroid, was shown to modulate the colony-stimulating factor-dependent clonal growth of myeloid progenitor cells in semisolid agar cultures, enhancing the formation of granulocyte colonies (50-100%) and suppressing the formation of macrophage colonies (75-97%). Modulation of the pattern of myeloid colony formation by dexamethasone (12-125 nM) was brought about when the steroid was administered to 6-day cultures at the time of culture initiation and up to 72 hr later. Dexamethasone inhibited myeloid cell proliferation when administered to 5-day liquid cultures at culture initiation and up to 96 hr later. Dexamethasone (12-250 nM) also enhanced the phagocytic activity of bone marrow-derived mononuclear phagocytes toward heat-killed (HK) yeast cells (up to 100%) and IgG-coated sheep red blood cells (up to 60%). Enhancement of the phagocytic capability depended critically on the stage in culture at which dexamethasone was administered. Exposure to dexamethasone for 28 hr up to 96 hr of 96-hr cultures of bone marrow cells did not lead to a modulation of phagocytic activity of the developing mononuclear phagocytes. The presence of dexamethasone during the critical period of 96 hr to 120 hr after culture initiation led to an enhanced phagocytic capability, which was statistically significant already 12 hr after the administration of the glucocorticoid. Dexamethasone induced an enhanced phagocytic activity when administered at any time after culture initiation provided that it was in culture during this critical period. When added at 120 hr of culture, dexamethasone no longer enhanced the phagocytic capability of mononuclear phagocytes and when added later than 156 hr of culture suppressed it. Dexamethasone also suppressed (up to 68%) the phagocytic capability of resident and elicited peritoneal macrophages. The results suggest that glucocorticoids shift the balance of granulocyte vs. macrophage formation at early stages of precursor cell differentiation. Reduction in mononuclear phagocyte growth and enhancement of its phagocytic capability might reflect accelerated differentiation/maturation steps. The inhibitory effect of dexamethasone on macrophage formation and on the phagocytic capability of mature mononuclear phagocytes and peritoneal macrophages might be a relevant aspect of the in vivo immune suppression encountered after glucocorticoid administration.

Immunocytochemical demonstration of tissue-type plasminogen activator in endocrine cells of the rat pituitary gland

We immunocytochemically stained rat pituitary glands using antibodies against plasminogen activators of the tissue type (t-PA) and the urokinase type (u-PA). A large population of endocrine cells in the anterior lobe of the gland displayed intense cytoplasmic immunoreactivity with anti-t-PA. In some areas of the intermediate lobe we found a weak staining, and we observed weakly staining granular structures in the posterior lobe. Controls included absorption of the antibodies with highly purified t-PA. In addition, SDS PAGE followed by immunoblotting of pituitary gland extracts revealed only one band with an electrophoretic mobility similar to that of t-PA when stained with anti-t-PA IgG. No u-PA immunoreactivity was detected in the rat pituitary gland. Sequential staining experiments using antibodies against growth hormone and t-PA demonstrated that the t-PA-immunoreactive cells constitute a large subpopulation of the growth hormone-containing cells. These findings represent the first direct evidence for the presence of t-PA in cell types other than endothelial cells in the intact normal organism. In this article we discuss the implications of the results for a possible role of t-PA in the posttranslational processing of prohormones.

Production of plasminogen activators by human T-cell leukaemia virus-transformed human T cell lines

Six human T cell lines HAMA, KUN, KAN, TCL-Haz, TCL-Ter, and TCL-Mor, which were transformed by a retrovirus, human T-cell leukaemia virus (HTLV), constitutively produced plasminogen activators (PAs) in culture supernatants. The amount of PAs produced varied among the cell lines. The PAs were distinguished by immunochemical analysis between two types: urokinase (UK)-type and non-UK-type. KUN, TCL-Ter, and HAMA mainly produced UK-type PA, whereas the other cell lines produced both types. Thus, HTLV-transformed T cell lines differ in the quality and quantity of the PAs they produce. The PAs in the culture supernatants of each cell line were separated into several mol. w forms on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The results indicate that the same cell line produces PAs of different mol. wt. PA production by these cell lines was affected by treatment with phorbol miristate acetate, concanavalin A, and phytohaemagglutinin; the effects were substantially different in each cell line. The data described here indicate that HTLV-transformed T cell lines constitutively produce PAs which are very heterogeneous in both quality and quantity.

Plasminogen activator is a mitogen for astrocytes in developing cerebellum

Newborn rat cerebellum microexplants cultured in Minimal Essential Medium with glucose and insulin released plasminogen activator (PA), which was detected in living cultures by a substrate overlay assay. Gel electrophoresis of cerebellum-conditioned medium followed by zymography resolved PA activity in two separate bands of 48,000 and 75,000 daltons apparent mol. wt. Using specific antisera, these bands were shown to be respectively urokinase and tissue-type PA. Cerebellum conditioned medium as well as purified human urokinase induced the proliferation and outgrowth of glial fibrillary acid protein-positive cells from newborn cerebellar microexplants. The effect was suppressed by the serine protease inhibitor phenyl methanesulfonylfluoride. Since PAs are most likely of neuronal origin, we suggest that at least one of these proteases acts as a neuronoglial mitogenic signal during development.

Effect of betamethasone on the dual reaction to anti-human IgE in man: influence of time interval between administration of drug and anti-IgE

The influence of the time interval between administration of a glucocorticoid, betamethasone, and anti-IgE on the effect of the drug on the early and late phase response (LPR) to anti-IgE was examined in 38 volunteers in a randomized controlled study. The immediate flare and wheal responses to intradermally (i.d.) injected anti-IgE were inhibited by approximately 20 and 30% respectively by a 10 day i.d. pretreatment period with repeated 50 micrograms doses (total 300 micrograms) of betamethasone (P less than 0.01), whereas responses to histamine were not influenced. A single i.d. injection of 50 micrograms betamethasone 24 h prior to anti-IgE challenge attenuated the wheal response (P less than 0.05), whereas injection of the drug 2 h prior to and together with anti-IgE had no influence on the early response. Corresponding LPRs were reduced approximately 30% throughout the observation period of 1-24 h (P less than 0.01). Injecting the drug i.d. 30 min following anti-IgE challenge had no significant influence on the total observation period (1-24 h) of the LPR but antagonized the LPR by 35% at 6-24 h (P less than 0.01). It is concluded that glucocorticoids inhibit IgE-dependent LPRs. When extending the topical pretreatment period with the compounds also the early part of the allergic reaction is attenuated.

Regulation of macrophage collagenase, prostaglandin, and fibroblast-activating-factor production by anti-inflammatory agents: different regulatory mechanisms for tissue injury and repair

Activation of macrophages results in the production of tissue destructive mediators and enzymes including prostaglandins (PGE) and collagenase. In addition, activated macrophages also generate mediators which enhance connective tissue formation through their effects on fibroblast growth. To determine whether the pro-inflammatory mediators and the mediator(s) involved in tissue repair are under the same regulatory control, guinea pig macrophage cultures were treated with various pharmacologic agents and their supernatants monitored for biologic activity. The nonsteroidal anti-inflammatory agent, indomethacin, and the glucocorticoid, dexamethasone, at pharmacologic concentrations inhibited not only prostaglandin synthesis (greater than 90%) but also the production of collagenase (greater than 90%). Colchicine, a microtubule disruptive agent, but not the inactive form, lumicolchicine, markedly diminished the production of collagenase independently of prostaglandin synthesis. In contrast to the inhibitory effects of these anti-inflammatory agents on PGE and collagenase production, indomethacin did not inhibit the production of macrophage-derived fibroblast-activating factor (FAF). Furthermore, dexamethasone at pharmacologic doses did not inhibit FAF production. Colchicine not only did not inhibit FAF, but frequently enhanced the appearance of FAF In the macrophage cultures. Thus, it appears that regulation of the production of PGE and collagenase is different than the regulation of FAF synthesis and therefore the production of these mediators can be differentially modulated. Such a dissociation may provide a basis for mononuclear cell-mediated fibroblast growth and tissue repair to occur independently of the release of PGE2 and collagenase and even following anti-inflammatory drug therapy.

Human macrophage activation. Modulation of mannosyl, fucosyl receptor activity in vitro by lymphokines, gamma and alpha interferons, and dexamethasone

We describe a sensitive assay to measure immune activation of human macrophages in cell culture. Freshly isolated blood monocytes from normal subjects lack the ability to endocytose and degrade mannosyl-terminated glycoconjugates via specific receptors, but acquired this activity after cultivation in autologous serum for approximately 3 d. Addition of specific antigen, purified protein derivative, or T cell mitogens to mononuclear cells prevented the appearance of macrophage mannosyl receptor activity and lymphokine, gamma-, and alpha-interferons selectively down-regulated receptor activity in monocyte-macrophage targets. The effects of antigen challenge and gamma-interferon on mannosyl receptors can be prevented by 10(-8) M dexamethasone. Dexamethasone also inhibited release of another macrophage activation marker, plasminogen activator, which was increased by both gamma- and alpha-interferons. These studies show that activation of human macrophages is regulated by opposing actions of lymphokines and glucocorticoids.

A cellular binding site for the Mr 55,000 form of the human plasminogen activator, urokinase

The secretion of plasminogen activators has been implicated in the controlled extracellular proteolysis that accompanies cell migration and tissue remodeling. We found that the human plasminogen activator urokinase (Uk) (Mr 55,000 form) binds rapidly, specifically, and with high affinity to fresh human blood monocytes and to cells of the monocyte line U937. Upon binding Mr 55,000 Uk was observed to confer high plasminogen activator activity to the cells. Binding of the enzyme did not require a functional catalytic site (located on the B chain of the protein) but did require the noncatalytic A chain of Mr 55,000 Uk, since Mr 33,000 Uk did not bind. These results demonstrate the presence of a membrane receptor for Uk on monocytes and show a hitherto unknown function for the A chain of Uk: binding of secreted enzyme to its receptor results in Uk acting as a membrane protease. This localizes plasminogen activation near the cell surface, an optimal site to facilitate cell migration.

Activation of macrophages

The role of macrophages is essential in the development of a normal immune response. Not only are these cells involved in the initiation of this response by presenting antigens to lymphocytes and by producing Interleukin I, but they also participate in the various phenomena of cellular co-operation and regulation. It is also evident that macrophages can act as cytotoxic effector cells, especially against micro-organisms and tumor cells. This last function is restricted to activated macrophages. The aim of this review is to summarize our present knowledge concerning this "macrophage activation".

Microassay for the photometric quantitation of cell-associated plasminogen activator using a chromogenic tripeptide substrate

Plasminogen activator (PA), a neutral protease whose primary function is to convert plasminogen to plasmin, is produced by various cells including macrophages, monocytes, endothelial cells, and tumor cells. This study reports the use of the chromogenic tripeptide substrate D-Val-Leu-Lys-p-nitroanilide (S-2251) and an automated microtiter plate reader spectrophotometer for the determination of PA activity in cells and fluids. There was a linear relationship between the time of incubation at 37 degrees C and the square root of the absorbance measured at 405 nm when urokinase was incubated with the substrate in the presence of plasminogen. There was no activity in the absence of plasminogen. The slopes of the lines (square root A 405/time) were directly related to the concentrations of urokinase, up through 0.05 CTA units. Using this assay, we determined the cellular activity of PA in human promyelocytic cells HL-60 (1.33 +/- 0.12 CTA units/mg), human monocytoid cells U937 (1.27 +/- 0.12 CTA units/mg), mouse myeloid leukemia cells RFM/UN (0.70 +/- 0.07 CTA units/mg), freshly isolated normal human monocytes (0.00 +/- 0.00 CTA units/mg), and human monocytes after 7 days in culture (5.66 +/- 0.38 CTA units/mg). There was a variable amount of activity expressed in freshly isolated cells or cell lysates of peritoneal macrophages from normal mice, or mice that had gotten intraperitoneal injections of peptone, thioglycollate, or NaIO4, but after 24 or 48 h of culture, these activities, in general, increased. Using this assay, PA levels in the euglobulin precipitates from human plasma prepared without venous occlusion (0.03 +/- 0.02 CTA units/mg protein) or after 5 min of venous occlusion of the arm (0.18 +/- 0.01 CTA units/mg) were comparable to those reported by others using different assays. Thus, this represents a simple, rapid, accurate assay of PA that should be useful to those in immunology, cell biology, and clinical medicine.

cDNA and gene nucleotide sequence of porcine plasminogen activator

We have isolated cDNA and genomic clones coding for porcine plasminogen activator (urokinase, uPA). The cDNA is 2375 nucleotides long: it consists of a 5'-non-coding region (104 nucleotides), an open reading frame of 1329 nucleotides, and 3'-non-coding region of 942 nucleotides apart from the poly A tail. The genomic segment corresponding to the transcribed sequence is 5.85 kb long; it is composed of 11 exons and 10 introns. The 5'-flanking genomic region contains a number of sequences of potential regulatory significance, including possible hormone receptor binding sites and a sequence which we tentatively propose may be involved in activation of transcription by cAMP. The full sequence of both cDNA and genomic clones, the latter including 1.3 kb of flanking region, is presented and discussed, and the deduced amino acid sequence compared with that of human uPA.

Plasminogen activator activity in differentiating leukemia cells

Plasminogen activator (PA) activity of human promyelocytic leukemia cell line HL-60 was assayed by following the conversion of plasminogen to plasmin and the plasmin-mediated hydrolysis of 14C-labeled globin. When HL-60 cells were induced to differentiate into macrophages by 12-O-tetradecanoyl-phorbol-13-acetate (TPA), cell-associated PA activity and secretion of PA into the conditioned medium increased profoundly. PA activity increased earlier and as a result of lower concentrations of TPA than the ability of the cells to adhere. Exposure to 10(-6)M dexamethasone did not prevent TPA-induced adherence and produced a slight inhibition of cellular PA activity. These findings imply that TPA-induced differentiation of HL-60 cells to macrophage-like cells is associated with induction of PA activity.

Functional characteristics of murine macrophages responding to migration inhibitory factors

Mouse bone marrow cells differentiate in culture in the presence of L cell-conditioned medium to macrophages (M phi). Proliferation, release of plasminogen activator, expression of transglutaminase, random motility and response to a standard preparation of purified M phi migration inhibitory factor (MIF) was recorded daily up to 14 days. After an initial phase of proliferation, precursor cells differentiated into M phi. In the course of maturation, plasminogen activator production was transiently expressed between day 4 and 12; beginning on day 5 the cells expressed intracellular transglutaminase. Random motility of cells was high at the beginning of culture but steadily declined thereafter. The response to MIF was only expressed between day 5 and 8. However, it was possible to induce MIF responsiveness in mature, unresponsive M phi by the addition of L cell-conditioned medium. To characterize the MIF-responsive M phi type further, bone marrow-derived M phi at day 6 of culture were separated on a hypotonic Percoll gradient into three distinct cell bands. While all densities of M phi displayed random migration, only cells with a density between 1.060 and 1.065 were responsive to MIF. We conclude that the response of M phi to MIF is a phenotypic trait transiently expressed in the course of maturation.

Cyclic nucleotides and their relationship to complement-component-C2 synthesis by human monocytes

The time courses of changes in cyclic nucleotide levels in monocytes have been studied. Histamine and prostaglandin E2 (PGE2) produced a rapid rise in cyclic AMP (peak 15 min) levels, which returned to normal within 4h, whereas cholera toxin, NaF and phosphodiesterase inhibitors produced slow sustained rises lasting over 24h. With the exception of isobutylmethylxanthine (10 mumol X 1(-1), none of these reagents altered cyclic GMP levels. alpha 1-Adrenergic and nicotinic cholinergic receptor-ligand interactions and imidazole produced rapid and relatively short-lived falls in cyclic AMP, and rises in cyclic GMP. In contrast, prostaglandin synthetase inhibitors produced delayed but more sustained falls in cyclic AMP but no rises in cyclic GMP. Agents that increased cyclic AMP decreased complement-component-C2 production, and those that decreased cyclic AMP increased C2 production. Agents that increased cyclic GMP alone (ascorbate, nitroprusside and prostaglandin F2 alpha) did not affect C2 production. Antigen-antibody complexes that stimulate C2 synthesis produced falls in cyclic AMP and rises in cyclic GMP similar to those produced by adrenergic and cholinergic ligands. Serum-treated complexes and anaphylatoxins, which inhibited C2 production, were associated with changes in cyclic AMP similar to those produced by histamine and PGE2. These data suggest that there are two transmembrane signals involved in the regulation of C2 production by monocytes. The inhibitory signal is adenylyl cyclase activation. The stimulatory signal is not so obvious, but may be Ca2+ influx, since the time courses of changes in cyclic nucleotides produced by agents that stimulate C2 synthesis are identical, and alpha 1-adrenergic agonists cause the formation of Ca2+ channels.

Effect of forskolin on prostaglandin synthesis by mouse resident peritoneal macrophages

The relationship between cyclic 3',5'-adenosine monophosphate (cAMP) and prostaglandin (PG) synthesis was investigated in the mouse resident peritoneal macrophage. Macrophages were established as monolayer cultures in petri dishes. After addition of various agents, culture media and cells were removed for PG and cAMP analysis by standard radiochromatographic techniques and radioimmunoassay respectively. Forskolin, a potent receptor-independent adenylate cyclase activator, rapidly increased cAMP synthesis within 5 min in a dose related fashion in both non-treated macrophages and macrophages treated with 12-O-tetradecanoylphorbol-13-acetate (TPA). Furthermore, forskolin markedly reduced both 6-keto-PGF1 alpha and PGE2 synthesis induced by TPA and this inhibition was inversely correlated with increases with cAMP generation. In contrast, cholera toxin failed to mimic the inhibitory action of forskolin on PG synthesis even though it induced similar increases in cAMP; however this increase was only evident after a lag period of at least 1 h. Additionally, forskolin, but no cholera toxin inhibited PG synthesis and zymosan phagocytosis when these cells were activated with zymosan particles. These observations, therefore, suggest that a rise in cAMP is not always correlated with a reduction in PG synthesis.

Stimulation of plasminogen activator in osteoblast-like cells by bone-resorbing hormones

Hormonal control of plasminogen activator (PA) was studied in clonal rat osteogenic sarcoma cells which are phenotypically osteoblast, and in osteoblast-rich rat bone cell cultures. The bone-resorbing hormones (parathyroid hormone, prostaglandin E2, epidermal growth factor and 1,25-dihydroxyvitamin D3) stimulated PA activity in both cell types. The relative efficacies of vitamin D metabolites and of prostanoids reflect their relative potencies as stimulators of bone resorption.

Induction of ornithine decarboxylase, RNA, and protein synthesis in macrophage cell lines stimulated by immunoadjuvants

Early biochemical changes associated with adjuvant stimulation of macrophage protein synthesis were studied using two murine macrophage cell lines, PU5-1.8 and J774.1. An induction of ornithine decarboxylase (ODC) was detected 2 hours after exposure of PU5-1.8 and J774.1 cells to two crude immunoadjuvants, BCG cell walls (BCGcw) and lipopolysaccharides from Escherichia coli (LPS). The chemically defined immunoadjuvant glycopeptide, N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDPL) also promoted an increase in ODC activity at 2 hours that was maximal after 4 hours, while little or no effect was observed with the D-alanyl analog (MDPD) that is devoid of adjuvant activity. The increase in ODC activity promoted by BCGcw in PU5-1.8 and J774.1 cells returned toward control levels by 6 to 8 hours. BCGcw also stimulated RNA and protein synthesis which remained elevated for at least 24 hours and was associated with a decrease in DNA synthesis and cell proliferation. ODC induction by BCGcw and MDPL was enhanced by the addition of PGE2 in both cell lines. Indomethacin slightly depressed the magnitude of ODC stimulation by BCGcw in J774.1 cells but failed to alter the response of PU5-1.8 cells. Additional observations indicated that the induction of ODC by BCGcw in both cell lines was preceded by an activation of cyclic AMP-dependent protein kinase. These observations suggest that a cyclic AMP-mediated induction of ODC may be an early biochemical marker of adjuvant stimulation in macrophages.

Connective tissue activating peptide III. Induction of synthesis and secretion of plasminogen activator by synovial fibroblasts

Connective tissue activating peptide III (CTAP-III) is a platelet factor that induces, in cultured connective tissue cells, activities observed in chronic inflammation. In this study we measured plasminogen activator secretion by synovial fibroblasts after stimulation by CTAP-III. Increased plasminogen activator secretion was observed 24-48 hours after stimulation. Induction was prevented by dexamethasone (10(-9)-10(-7) M), cycloheximide (1 microgram/ml) and, variably, by actinomycin D (0.3 microgram/ml), but not by cytosine arabinoside (10(-4)M). This is the first evidence that CTAP-III induces degradative as well as proliferative activity by connective tissue cells.

Concomitant secretion of prourokinase and of a plasminogen activator-specific inhibitor by cultured human monocytes-macrophages

The plasminogen activator (PA) produced by freshly purified human monocytes-macrophages and histiocytic, lymphoma-derived U 937 cells was analyzed by zymography after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and found to migrate with an apparent Mr of 55,000, identical to that of urokinase (Uk). By immunoprecipitation with antibodies specific for the two different types of PA, the enzyme was shown to be immunologically related to urokinase, and not to tissue PA. Urokinase was secreted in the form of the inactive Mr 55,000 zymogen prourokinase , and could be converted to the active Mr 55,000 enzyme by limited proteolysis with plasmin. Conditioned media from cultures of U 937 cells and monocytes-macrophages inhibited the fibrinolytic activity of exogenously added urokinase. Using [125I]-labeled urokinase we observed the formation of an enzyme-ligand complex, which was not dissociated by boiling in SDS and migrated with an apparent Mr 40,000 daltons higher than the free enzyme; since complexed urokinase was functionally inactivated as a PA, the ligand is an inhibitor of urokinase. This inhibitor is different from fibroblast-produced protease- nexin , in that it did not interact with thrombin. These results suggest that plasminogen activation by mononuclear phagocytes can be modulated through the secretion of both (pro)enzyme and a specific inhibitor.

Human endothelial cells contain one type of plasminogen activator

At least two types of animal plasminogen activating enzymes exist, differing in amino acid sequence, molecular mass and immunological reactivity: the urokinase-type and the tissue-type plasminogen activators. By affinity chromatography with monoclonal antibodies, we have purified the human activators of both types to homogeneity. Using immunocytochemistry with rabbit antibodies raised against these preparations, we now demonstrate that the plasminogen activator present in endothelium of veins and other blood vessels is of the tissue-type. No urokinase-type plasminogen activator immunoreactivity was detected in endothelial cells in the intact organism. These findings support the assumption that mobilization of plasmin for different purposes may involve different types of plasminogen activators, and that the plasminogen activator involved in thrombolysis is of the tissue-type.

Distribution of urokinase-type plasminogen activator immunoreactivity in the mouse

Immunocytochemistry, using rabbit antibodies to a urokinase-type 48-Kdalton Mr mouse plasminogen activator, showed that enzyme immunoreactivity is widely distributed in the normal mouse. Strong staining was obtained in widely disseminated connective tissue cells with a fibroblast-like morphology. Such cells occurred in high numbers in the lamina propria mucosae of the gastrointestinal tract, and in moderate numbers in the connective tissue septa of the pancreas. A few such cells were detected around the larynx, trachea, and bronchi. Immunoreactivity also occurred in epithelial cells of the proximal and distal kidney tubules, the ductus deferens, and in pulmonary pneumocytes. In addition, presumably extracellular staining was seen irregularly along the basement membrane and fibrillar structures in the lamina propria of the small and large intestines. Moreover, decidual cells of the mouse placenta stained strongly, and a moderate staining was observed in epithelial cells of involuting mammary glands, but not in those of noninvoluting glands. No immunoreactivity was observed in endothelial cells. Control experiments included absorption of the antibodies against highly-purified mouse plasminogen activator and the corresponding proenzyme, and the finding of a good correspondence between the number of immunoreactive cells and measurable enzymatic activity determined in adjacent tissue sections. Separation by SDS PAGE followed by immunoblotting revealed only one immunochemically stainable protein band with Mr approximately 48 Kdaltons in extracts from tissues showing immunoreactivity.

Reverse fibrin autography: a method to detect and partially characterize protease inhibitors after sodium dodecyl sulfate--polyacrylamide gel electrophoresis

A new technique, reverse fibrin autography, was developed to detect protease inhibitors previously fractionated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Exogenous proteases were incorporated into fibrin-agar indicator films, eventually causing the fibrin to lyse. When an acrylamide gel containing inhibitors was placed on top of such an indicator, the positions of the inhibitors were revealed by the formation of opaque, lysis-resistant zones in the otherwise cleared fibrin film. The technique was versatile in that a variety of inhibitors were revealed, and semiquantitative since the size of the lysis-resistant zone in the indicator increased in proportion to the amount of inhibitor subjected to electrophoresis. This approach could be used not only to detect inhibitors having different protease specificities, but also to distinguish between the inhibitor activities of antibodies directed against urokinase or tissue-type plasminogen activator. Thus, reverse fibrin autography offers a convenient new approach to rapidly screen and partially characterize inhibitors present in complex biological samples.

Sitosterol-stimulative production of plasminogen activator in cultured endothelial cells from bovine carotid artery

The endothelial cell is a rich source of plasminogen activator that is associated with fibrinolytic activity in blood vessel. Addition of sitosterol to the culture medium of endothelial cells from bovine carotid artery gave rise to a marked increment in the activity of plasminogen activator. Removal of sitosterol from the culture medium resulted in a decrease of plasminogen activator activity back to normal levels. Enhancement of plasminogen activator activity in cultured endothelial cells was not observed by cholesterol, 5-androsten-3 beta-ol and others.

Inhibition of the late phase reaction to anti-human IgE in man by oral tranexamic acid

Pharmacological modulation of the immediate and late phase reaction (LPR) to anti-human IgE was further investigated in a double-blind cross-over study. Tranexamic acid (AMCA) 1 g t.i.d. 24 h prior to and following intradermal injection of anti-IgE produced an approximate 40% inhibition of the LPR (P less than 0.01) without affecting the early response as compared with placebo in 10 volunteers. Antagonistic effect on activation of fibrinolysis and possibly the complement system is suggested as a possible mode of action.

Evidence for an extracellular plasmin-dependent proteolytic system in mineralizing matrices

Plasminogen activator, which specifically catalyzes the extracellular conversion of plasminogen to plasmin, was identified in the cell-free mineralizing matrices of enamel, dentin, cementum, and bone by a fibrinolytic overlay technique. The spatial separation in developing teeth of successive stages of dentinogenesis allowed us to identify predentin as a major site of plasminogen activator activity. In addition, plasminogen, the natural substrate for the activator, was demonstrated in predentin by immunohistochemical techniques. Extraction of human dentin/predentin with neutral demineralizing buffers solubilized the activator along with inhibitory components capable of blocking the activation of plasminogen. When resolved by polyacrylamide electrophoresis under dissociative conditions, however, the activator emerged in active form as two closely spaced bands at Mr 66,000 and 62,000. In the mineralizing enamel matrix of continuously forming rodent incisors, activator activity was limited to a 3-5 mm wide segment which marks the transition between "soft" and "chalky" enamel, whereas the entire overlying enamel organ was rich in activator activity at all developmental stages. This suggests that the activator is transported to the enamel matrix only in a narrow zone which coincides with the most rapidly mineralizing site. The coincident expression of plasminogen activator activity and mineral accretion suggests that plasmin-dependent proteolysis may play a role in the extracellular regulation of matrix mineralization.

Involvement of prostaglandins in LPS-mediated regulation of plasminogen activator synthesis by inflammatory macrophages

We have previously shown that production of plasminogen activator by inflammatory macrophages can be inhibited by immunomodulators of bacterial origin, especially LPS. In these experiments, the contribution of prostaglandins to this control was investigated. We examined the effect of two prostaglandin synthetase blockers, indomethacin and diclofenac. These drugs do not modify per se the production of plasminogen activator but they can partially prevent the inhibitory effect of LPS. Since restoration was not complete when plasminogen activator production was strongly inhibited, it is suggested that the immunomodulator acts through a mechanism involving more than one pathway only one of which would be mediated by prostaglandins.

Antibodies to plasminogen activator inhibit human tumor metastasis

The human carcinoma HEp3 grows on the chorioallantoic membrane and metastasizes to the chicken embryo with kinetics that are quantitatively predictable. We have used this experimental system to test whether plasminogen activator produced by the tumor is required for metastasis. Rabbit antibodies were raised against human urinary urokinase; these cross-reacted with and blocked the catalytic activity of HEp3-PA but did not inhibit chicken PA. When administered intravenously to embryos that had received an inoculum of HEp3 cells, the anti-urokinase antibodies did not inhibit tumor growth at the site of primary inoculation on the chorioallantoic membrane, but they either prevented or strongly inhibited metastasis to the embryo lung. Antibody treatment delayed the onset of pulmonary metastasis, indicating that plasminogen activator is required during early stages of the process.

Plasminogen activator in the developing rat cerebellum: biosynthesis and localization in granular neurons

The histochemical localization of plasminogen activator (PA) and the level of the translatable mRNA species coding for active PA were analyzed during ontogenesis of normal and of irradiation-agranulated rat cerebellum. Autoradiographic localization of PA activity was performed by plasminogen-dependent fixation of [125I]fibrin degradation products to frozen sections of developing rat cerebellum. Both the immature external and the adult internal granular layers were intensely labeled, in addition to labeling of meninges. In the irradiation-aggranulated cerebellum, PA labeling could be observed in residual granular neurons which went through their final division prior to the irradiation protocol. The concentration of the mRNA species directing the synthesis of catalytically active PA (PAmRNA) was monitored by an in ovo bioassay, using Xenopus oocytes as a translation system. A major species of 80,000 and a minor species of 50,000 apparent molecular weight of active PA were translated by mRNA from either control or X-irradiated cerebellum throughout ontogenesis. These could be detected by electrophoretic analysis of extracts and incubation media of microinjected oocytes. Both the content and the concentration of PAmRNA were found to be the highest at the stage of cerebellar development when granular neurons proliferate and migrate. These observations suggest that a major portion of the PA activity in the rat cerebellum is synthesized and localized in granular neurons through cerebellar ontogenesis, and that PA activity in the developing cerebellum is largely determined by the level of translatable mRNA coding for this enzyme.

Plasminogen activator in cultured human epidermal cells

Primary cultures of human epidermal cells produce plasminogen activator (PA) as demonstrated by the ability of conditioned medium or cell lysates to hydrolyze fibrin in the presence of plasminogen, and to cleave [125I]plasminogen to characteristic fragments. The major molecular species of PA in human epidermal cells was inhibited by diisopropylfluorophosphate and comigrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with the high molecular weight band of human urokinase (Mr 55,000). Production of PA by human epidermal cells was inhibited by cycloheximide, stimulated by colchicine, and not affected by cytochalasin B or the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. Both cholera toxin and epidermal growth factor stimulated PA activity in human epidermal cells, and PA activity was maximal at concentrations that best support in vitro growth of human epidermal cells. Examination of individual cells indicated that at least 15% of cells within a culture produced detectable amounts of PA.

The effect of mouse hepatitis virus infection on the microcirculation of the liver

Mouse hepatitis virus type 3 infection results in strain-dependent liver disease. The effects of mouse hepatitis virus type 3 on the microcirculation of the liver in both fully susceptible (Balb/cJ) and fully resistant (A/J) mice were studied. In Balb/cJ mice, 6 to 12 hr following infection, abnormalities in liver blood flow were observed which consisted of granular blood flow in both terminal hepatic and terminal portal venules. In addition, sinusoidal microthrombi were present predominantly in periportal areas. By 24 to 48 hr, liver cell edema and small focal lesions were prominent. At 48 hr, thrombi and hepatocellular necrosis were widespread, and blood was shunted from damaged areas into patent sinusoids. In sharp contrast to these abnormal findings, normal streamlined blood flow was present in the resistant A/J animals at all time points following infection. Since large amounts of virus were demonstrated by immunofluorescene in and by recovery and growth from livers of both resistant and susceptible strains, the presence of the virus per se cannot explain the abnormalities observed.