Thrombin enhances production and release of tissue plasminogen activator from bovine venous endothelial cells

The effects of ginseng radix rubra on human vascular endothelial cells

The effect of Ginseng Radix Rubra (Red ginseng) on human vascular endothelial cells was examined. Red ginseng was found to promote the proliferation of vascular endothelial cells, inhibit the production but promote the decomposition of endothelin, which is known to constrict blood vessels and raise blood pressure as well as accelerated the synthesis of nitric oxide, which is known to have an angio-tonic effect. Furthermore, Red ginseng was observed to increase the production of Interleukin 1 beta, which is known to play important roles in the homeostatic activities of the human body such as immunity and inflammation as well as increasing the production of tissue plasminogen activators, which suppress the formation of thrombin in the blood coagulation and fibrinolysis mechanisms. It is suggested that Red ginseng has the effect of accelerating endothelial cells proliferation and of promoting physiological activities.

Phorbol 12-myristate 13-acetate stimulates the release of glycosaminoglycans from cultured vascular endothelial cells: possible involvement of protein kinase C activation

We investigated the release of glycosaminoglycans (GAGs) labeled with [3H]glucosamine and [35S]sulfate into the medium from cultured bovine aortic endothelial cells stimulated by phorbol 12-myristate 13-acetate (PMA) which is an activator of protein kinase C (PKC). The GAG release was significantly accelerated by PMA without an increase in the leakage of lactate dehydrogenase but was unchanged by 4 alpha-phorbol 12,13-didecanoate which lacks the ability of PKC activation. The acceleration of GAG release by PMA was strongly suppressed by a PKC inhibitor H-7 but not by HA 1004 which is an inactive analogue of H-7. Characterization of GAGs released into the medium revealed that PMA increased both heparan sulfate and the other GAGs in a similar degree. Although the release of GAGs stimulated by thrombin was also suppressed by another PKC inhibitor staurosporine, stimulation by plasmin was unaffected by the inhibitor. The present data suggest that protein kinase C mediates the release of endothelial cell GAGs including anticoagulant heparan sulfate and the stimulation of the release by thrombin includes this mechanism.

Morphological and hemostatic changes in rats with abdominal arterial prosthesis

We evaluated the changes over time in hemostatic factors during ongoing arterial thrombosis in rats, as induced by a loop-shaped aortic prosthesis. Moreover, we investigated this condition by inspecting in parallel local thrombus growth, systemic vascular prostacyclin and t-PA production. One minute after loop insertion, activated platelets spread on the internal surface of the prosthesis and 24 hrs later numerous platelet aggregates supported by a fibrin network could be observed. However, no evidence for platelet activation could be concomitantly found in peripheral blood. A sustained increased in PGI2 formation was detected together with a progressive increase in plasma fibrinolytic activity during thrombus growth. The levels of fibrinogen as well as antithrombin III (ATIII) and heparin cofactor II (HCII) activities were steadily increased in loop-bearing animals. In conclusion, the dynamic phases of thrombus formation, in an aortic prosthesis, produce changes in vascular function and in hemostatic factors at the level of systemic blood.

Zinc-induced tolerance to cadmium cytotoxicity without metallothionein induction in cultured bovine aortic endothelial cells

We investigated the cytotoxicity of cadmium in cultured vascular endothelial cells from bovine aorta pretreated with zinc. The cytotoxicity was evaluated by the [3H]adenine release assay. It was shown that the increase in the [3H]adenine release after challenge with cadmium was significantly prevented by pretreatment with zinc. It was histologically observed that cadmium-induced occurrence of the de-endothelialized areas was reduced in zinc-pretreated cell layer. Intracellular accumulation of cadmium was significantly less but that of zinc was more in zinc-pretreated cells. The content of cadmium in both the particulate and the cytosol fraction was decreased by zinc pretreatment; however, metallothionein content after challenge with cadmium was not changed. It was therefore concluded that zinc is capable of inducing a tolerance to cadmium cytotoxicity in cultured vascular endothelial cells; this tolerance is postulated to be due to a decrease in the intracellular cadmium accumulation rather than a metallothionein induction.

Thrombin induced cytoskeletal change in cultured bovine corneal endothelial cells mediated via protein kinase C pathway

We studied the participation of the protein kinase C pathway in thrombin-induced cytoskeletal alterations in confluent cultured bovine corneal endothelial (BCE) cells. Cultured BCE cells were exposed to alpha-thrombin (0.1-10 U/ml for 15-60 min) and the distribution of F-actin and vinculin plaques was examined using immunofluorescent staining and electron microscopy. Phorbol 12-myristate 13-acetate (PMA, 10 nM for 15 min), the broad spectrum protein kinase inhibitors staurosporine (10 nM) and H-7 (10 nM), and highly specific PKC inhibitor calphostin C (10 nM) were used to evaluate the role of PKC/phosphorylation in this phenomenon. HA-1004 (10 nM) was used as a negative control for these inhibitors. In a parallel experiment, PKC activity of cytosol and membrane of BCE cells was also evaluated. In control samples, F-actin was distributed mainly at the periphery of cells, where it formed dense peripheral bundles; vinculin plaques were also present at the cell boundary. Exposure of BCE cells to thrombin changed the distribution of F-actin and vinculin into a diffuse pattern; a similar alteration was also induced by incubation with PMA. These phenomena were blocked by incubation with H-7, staurosporine and calphostin C. Both cytosolic and membrane PKC activity was increased after 5 to 30 min exposure of alpha-thrombin and returned to the control level after 1 h. alpha-Thrombin induces alteration in the cytoskeleton of BCE cells, and this message is transduced at least in part by PKC dependent pathways. PKC/phosphorylation may thus play an important role in physiological processes that involve alterations of the cytoskeleton.

Cadmium-induced alteration of glycosaminoglycans with an enhancement of heparin-like activity in cultured vascular endothelial cells

Glycosaminoglycans (GAGs), especially heparan sulfate, are involved in the anticoagulant property of vascular endothelium. It was observed that heparin-like activity on the surface of cultured bovine aortic endothelial cells was enhanced by cadmium at 1.0 microM or more after a 24-h incubation. The incorporation of [3H]glucosamine into GAGs, a marker of GAG synthesis, was markedly increased by cadmium at 0.5 microM or more in both the cell layer and the conditioned medium; however, the incorporation of [35S]sulfate, a marker of the GAG sulfation, was significantly reduced by the metal at 2.0 microM or more. Similar changes were observed in a cultured human umbilical vein endothelial cell layer. Characterization of GAGs in bovine endothelial cell layer revealed that cadmium (2.0 microM)-induced alterations mostly occurred in the major component heparan sulfate rather than in other minor GAGs. Stimulation of [3H]glucosamine incorporation by cadmium at 2.0 microM occurred even in the presence of p-nitrophenyl-beta-D-xyloside but disappeared in the presence of cycloheximide, suggesting that cadmium might induce the production of proteins which are involved in GAG synthesis. The present data suggest that vascular endothelial cells are capable of enhancing the potential anticoagulant activity on their surface via induction of heparan sulfate synthesis. This response of endothelial cells may be a defensive one to the procoagulant state of blood which can be induced by cadmium.

Plasmin-induced reduction of heparan sulfate in cultured vascular endothelial cell layer

Plasmin-induced alteration of glycosaminoglycans (GAGs) was investigated using a cell culture system of vascular endothelial cells derived from bovine aorta. In the cell layer, the incorporation of [3H]glucosamine into GAGs, a marker of the sugar chain formation, was slightly decreased by plasmin. On the other hand, the incorporation of [35S]sulfate, a marker of the sulfation, was markedly decreased by the protease. Plasminogen also induced a weak but similar change. Characterization of the cellular GAGs showed that plasmin inhibited the incorporation of both [3H]glucosamine and [35S]sulfate into the major component heparan sulfate at a similar degree. In the other GAGs, the [35S]sulfate incorporation was significantly decreased by plasmin without a change of the [3H]glucosamine incorporation. The leakage of lactate dehydrogenase from the endothelial cells was significantly increased by plasmin, suggesting that the protease exhibited cytotoxicity. The present data suggest that the anticoagulant activity on the surface of vascular endothelium mediated by the anticoagulant heparan sulfate may be reduced by plasmin which will be generated from plasminogen by plasminogen activators derived from endothelial cells.

Transforming growth factor beta-induced tolerance to cadmium cytotoxicity in cultured vascular endothelial cells

We investigated whether or not transforming growth factor beta (TGF beta 1) affects the sensitivity to cadmium of bovine aortic endothelial cell in a culture system. Cadmium cytotoxicity was evaluated by [3H]adenine release assay. It was found that pretreatment with recombinant human TGF beta 1 (rhTGF beta 1) of the confluent cultures resulted in a reduction of cadmium cytotoxicity, suggesting that the cytokine induced a tolerance to cadmium in the cells. Such a tolerance was induced slightly by either recombinant human tumor necrosis factor alpha or recombinant human basic fibroblast growth factor but not by recombinant human interleukin-1 beta and -6; rhTGF beta 1 was the most potent inducer. rhTGF beta 1 failed to induce the tolerance in the presence of anti-rhTGF beta 1 antibody. Pretreatment with the antibody alone caused a significantly sensitive response to cadmium, suggesting that endogenous TGF beta 1 can physiologically contribute to protection against cadmium cytotoxicity in endothelial cells. The accumulation of cadmium was increased in the extracellular fraction but significantly decreased in the intracellular fraction of the cells by pretreatment with rhTGF beta 1. The cadmium content was significantly decreased in the particulate fraction but not in the cytosol fraction. Gel filtration chromatography of the cytosol fraction revealed that cadmium was bound to high-molecular-weight protein and metallothionein; both peaks were slightly increased by pretreatment with rhTGF beta 1. It was concluded that rhTGF beta 1 induces a tolerance to cadmium in cultured endothelial cells, caused by a decrease in the cadmium accumulation in the particulate fraction of the cells. TGF beta 1 may serve as a protective factor against cadmium cytotoxicity in vascular endothelial cells.

Basic fibroblast growth factor suppresses tissue plasminogen activator release from cultured human umbilical vein endothelial cells but enhances that from cultured human aortic endothelial cells

Since basic fibroblast growth factor (bFGF) modulates the functions of vascular endothelial cells, we hypothesized that this factor may be involved in the regulation of the blood coagulation-fibrinolytic system mediated by the cells. Confluent cultures of vascular endothelial cells from human umbilical vein were treated with recombinant human bFGF (bFGF) in a serum-free medium and the content of tissue plasminogen activator antigen (t-PA:Ag) in the medium was determined by EIA. Treatment with bFGF resulted in a significant decrease in the release of t-PA:Ag from the cells accompanied with a less t-PA activity in the medium. In contrast, the t-PA:Ag release from human aortic endothelial cells was significantly increased by bFGF. The bFGF-induced decrease in the t-PA:Ag release from the venous endothelial cells was completely blocked by anti-bFGF antibody. The incorporation of [3H]leucine into the acid-insoluble fraction of the cells was significantly increased by bFGF; however, the activity of lactate dehydrogenase leaked into the medium was significantly decreased, suggesting that the suppression of the t-PA:Ag release caused by bFGF in the venous endothelial cells was not due to either a nonspecific inhibition of protein synthesis or a nonspecific cell damage. Since bFGF is postulated to be released from damaged endothelial cells, the present data suggest the regulation by bFGF of hemostasis mediated by endothelial cells when the vascular endothelium was damaged.

Stimulation by zinc of cultured vascular endothelial cell proliferation: possible involvement of endogenous basic fibroblast growth factor

Vascular endothelial cells from bovine aorta were cultured with zinc sulfate (20 microM or less) for 24 h and labeled with [3H]thymidine or [14C]leucine during the last 3 h of the culture. It was found that the cell number was significantly increased by zinc alone; the incorporation of both [3H]thymidine and [14C]leucine was also stimulated by the metal. The stimulation by zinc occurred in the presence or absence of exogenous basic fibroblast growth factor (bFGF). However, other heavy metals including copper, manganese and nickel did not exhibit such a stimulatory effect, suggesting that zinc plays a particular role in endothelial cell proliferation. Stimulation of the [3H]thymidine incorporation by zinc disappeared in the presence of either cycloheximide or anti-bFGF IgG; in addition, a lipoxygenase inhibitor nordihydroguaiaretic acid diminished the zinc stimulation but a cyclooxygenase inhibitor indomethacin did not exhibit such an inhibitory effect. These results indicated that zinc stimulated the proliferation of endothelial cells through the lipoxygenase pathway which mediates the stimulation by endogenous bFGF. In other words, the metal may amplify the endogenous bFGF-dependent proliferation of the cells.

Glomerular fibrinolytic activity in anti-GBM glomerulonephritis in rabbits

Fibrin is an important mediator of injury in severe proliferative forms of glomerulonephritis (GN). Normal glomeruli express fibrinolytic activity, which may protect against the injurious effects of fibrin deposition. Changes in glomerular fibrinolytic activity (GFA) may play an important role in modulating fibrin accumulation in GN. To study the changes in GFA associated with fibrin deposition in GN, autologous phase anti-glomerular basement antibody initiated GN (anti-GBM GN) was studied in rabbits. Net GFA was significantly reduced in association with glomerular fibrin deposition (1.3 +/- 0.8 ng fibrin lysed/10(3) glomeruli/2 hr, normal 57.1 +/- 25.4 ng fibrin lysed/10(3) glomeruli/2 hr, P < 0.02). Reduced GFA in fibrin associated GN was associated with decreased expression of tissue type plasminogen activator (tPA) and increased expression of plasminogen activator inhibitor type-1 (PAI-1) and glomerular macrophage infiltration. In a fibrin independent model of anti-GBM induced GN (heterologous phase), with equivalent injury (proteinuria), net GFA was increased (174 +/- 64 ng fibrin lysed/10(3) glomeruli/2 hr). This was associated with increased tPA and uPA, and decreased PAI-1 in the absence of significant macrophage infiltration. These studies demonstrate that fibrin deposition in GN is associated with a net reduction of GFA, attributable to reduced expression of plasminogen activators and augmentation of PAI-1. Reduction of GFA may potentiate glomerular fibrin deposition and consequent glomerular injury. The association between glomerular macrophage influx and reduction in GFA suggests that this change may be directed by macrophages.

Possible mechanism for zinc protection against cadmium cytotoxicity in cultured vascular endothelial cells

We investigated the effect of zinc on cadmium cytotoxicity in vascular endothelial cells in a culture system. The cytotoxicity was evaluated by [3H]adenine release assay. Cadmium at 2 microM concentration and above significantly increased the [3H]adenine release, but zinc at 80 microM and below did not induce such a response after a 24-h incubation. Metallothionein was induced by cadmium at 0.1 microM and above but not by zinc at 300 microM and below; however, zinc at 10 microM and above significantly decreased cadmium-(2 and 5 microM) induced cytotoxicity. Zinc protection against cadmium cytotoxicity was also observed in the presence of 1 microM cycloheximide. Zinc caused significantly less accumulation of cadmium in the cell layer accompanied with a significant accumulation of zinc. The distribution (%) of cadmium in the particulate fraction of the cells was significantly decreased by zinc. In contrast, cadmium in the cytosol fraction was increased in the cells treated with both cadmium and zinc. Gel filtration chromatography of the cytosol showed that cadmium was capable of being bound to high-molecular-weight proteins and metallothionein. The metallothionein-bound cadmium was not increased by zinc; however, the relative distribution of cadmium in the high-molecular-weight fraction in the cytosol was decreased in cadmium plus zinc-treated cells. From these results, it was suggested that the mechanism by which zinc protects endothelial cells from cadmium cytotoxicity was decreased accumulation of cadmium in the particulate fraction and in the high-molecular-weight fraction in the cytosol of the cells. This alteration is postulated to be caused by both zinc-induced decrease in the intracellular cadmium accumulation and the sequestration of cadmium by cadmium-induced metallothionein.

Protective effect of copper against cadmium cytotoxicity on cultured vascular endothelial cells

We investigated the effect of copper on cadmium-induced cytotoxicity on vascular endothelial cells from bovine aorta in a culture system. Cytotoxicity was evaluated by the [3H]adenine release assay and the histological observation. After a 24-h incubation, cadmium exhibited a significant cytotoxicity on confluent cultures of endothelial cells in a dose-dependent manner, while copper only slightly did after a 24-h incubation. It was found that copper (5 microM) significantly decreased cadmium (1 and 2 microM) cytotoxicity; histologically, formation of de-endothelialized areas in the cell layer caused by cadmium was reduced by copper. The accumulation of cadmium in the cell layer was significantly decreased by copper; however, that of copper was unaffected by cadmium. It was therefore suggested that copper significantly protects cadmium-induced cytotoxicity on cultured endothelial cells primarily through decreasing the cellular cadmium accumulation.

YIGSR, a synthetic laminin peptide, inhibits the enhancement by cyclophosphamide of experimental lung metastasis of human fibrosarcoma cells

Tumor cells must attach themselves to basement membranes, through which they degrade and migrate, in order to spread to distant sites. If vascular endothelial cells are damaged by pretreatment with anticancer drugs and the subendothelial basement membranes are exposed, the attachment of malignant cells to basement membranes and subsequent metastasis formation in some tissues may be enhanced. In this study, the pretreatment of endothelial cell monolayers and mice with cyclophosphamide (CPA) was respectively shown to promote the adhesion of HT1080 human fibrosarcoma cells to endothelial cell monolayers in vitro and lung colonization in vivo. YIGSR, a synthetic laminin pentapeptide, inhibited the enhancement of lung colonization by CPA when it was co-injected intravenously with tumor cells. This inhibitory effect of YIGSR may be due to a reduction in the adhesion of HT1080 cells to injured blood vessel walls since YIGSR inhibited both the adhesion of HT1080 cells to CPA-treated endothelial cell monolayers and the invasion through basement membranes in vitro.

Plasmin stimulates the release of dermatan sulfate from vascular smooth muscle cells in culture

We investigated the effect of plasmin on the release of sulfated glycosaminoglycans (GAG) from cultured vascular smooth muscle cells. Confluent cultures of vascular smooth muscle cells from bovine aorta were labelled with [35S]sulfate and incubated at 37 degrees C for principally 60 min in a serum-free medium in the presence of plasmin. Plasmin at 10 mU/ml (approximately 2.7 micrograms/ml) and above significantly increased the release of [35S]sulfate-labeled GAG (35S-GAG) from the cell layer after a 60 min incubation. A time course study showed that plasmin at 10 mU/ml significantly increased the 35S-GAG release after 20 min and longer. However, plasminogen at 100 mU/ml and below did not cause a significant change of the 35S-GAG release after a 90 min incubation. A characterization of 35S-GAG revealed that plasmin increased both dermatan sulfate and the other 35S-GAG in the medium. Plasmin at 100 mU/ml enhanced the cell detachment significantly but only slightly. From these results, it was suggested that a endogenous thrombin inhibitor heparin cofactor II may be activated in the liquid phase by dermatan sulfate released from plasmin-stimulated vascular smooth muscle cells when the vascular is disrupted and plasma is exposed to extravessel.

Effect of cadmium on the monolayer maintenance of vascular endothelial cells in culture

We investigated the effect of cadmium on the maintenance of the monolayer of vascular endothelial cells to clarify a possible involvement of endothelium injury in cadmium-induced vascular disorders. Endothelial cells from bovine aorta were cultured with cadmium chloride (0.5, 1.0, 2.0 or 5.0 microM) for 24 or 72 h. A histological observation revealed that a de-endothelialized space was formed in the monolayer by cadmium treatment; the number of endothelial cells was significantly decreased by the metal. Cadmium significantly decreased the number of growing endothelial cells with a significant decrease in the [3H]thymidine incorporation, suggesting that cadmium inhibited the cell proliferation. On the other hand, cadmium significantly increased the detachment of [3H]thymidine-labeled endothelial cells from the monolayer with a parallel increase in the lactate dehydrogenase activity in the medium. From these results, it was suggested that cadmium impairs the endothelial cell monolayer; the de-endothelialized space was formed by both an increase in the cell detachment by cadmium cytotoxicity and a retardation of the repair of the space which was due to an inhibition of the cell proliferation caused by the metal.

Extracellular and cell-associated localizations of plasminogen activators and plasminogen activator inhibitor-1 in cultured endothelium

The extracellular localizations of urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (tPA), and plasminogen activator inhibitor-1 (PAI-1) were examined in cultured bovine capillary endothelial cells (BCEs) by an immunofluorescence method using BCEs treated with or without saponin and focal contact preparations. The specific immunofluorescence of cell surface uPA showed a patchy or strand-like distribution and was colocalized with vinculin strands indicating that uPA secreted from BCEs was mainly deposited at the cell surface of focal contacts. BCEs at a subconfluent density showed a higher intensity of specific immunofluorescence for uPA than when they were at a confluent density. tPA was observed over the dorsal surface of cultured BCEs and accentuated at their margins, suggesting that tPA was diffusely distributed on the luminal surface of BCEs in vivo. PAI-1 was distributed in the extracellular matrix under cultured BCEs. These findings suggest that uPA and PAI-1 are located under BCEs participating in the regulation of proteolytic activities provoked by plasminogen-PAs-plasmin system in vivo. The localization of tPA appears to be consistent with its function, which is to maintain the fluidity of the blood and to initiate thrombolysis in vivo.

Effect of thrombin on the production of glycosaminoglycans by cultured endothelial cells

We investigated the effect of thrombin on the production process of glycosaminoglycans (GAG) in cultured bovine aortic endothelial cells. It was revealed that the trichloroacetic acid-insoluble [35S]sulfate-labeled GAG (35S-GAG) was decreased by thrombin. The thrombin-induced decrease in the accumulation of 35S-GAG in the cell layer occurred even in the presence of actinomycin D or cycloheximide. The incorporation of both [35S]sulfate and [3H]glucosamine into the GAG was decreased by thrombin, while the ratio of 35S to 3H was not changed. Also, the incorporation of both [3H]glucosamine and [14C]UDP-xylose into the GAG was inhibited by thrombin. From these results, it was suggested that thrombin decreased GAG in the endothelial cell layer through an suppression of formation of polysaccharide chains rather than that of core protein.

Inhibitory effect of rhodamine B on the proliferation of human lip fibroblasts in culture

The effect of the cosmetic dye rhodamine B on the proliferation of human lip fibroblasts (KD cells) was investigated in a culture system. Rhodamine B at 25 micrograms/ml and above significantly decreased the number of the cells after a 72 h culture. A time course study revealed that 50 micrograms/ml of rhodamine B-induced decrease in the cell number occurred after 48 h and longer, suggesting that the dye inhibited cell proliferation without a decrease in cell attachment. The detachment of [3H]thymidine-labeled cells from the monolayer was unaffected by rhodamine B at 100 micrograms/ml and below. The incorporation of [3H]thymidine and [14C]leucine into the acid-insoluble fraction of the cell layer was significantly inhibited by 50 micrograms/ml rhodamine B treatment. Histologically, the damage of KD cells was not marked, however, a degenerative change of nuclei and an irregular shape of the cells as well as a decrease in the cell number were caused by 50 micrograms/ml rhodamine B. Rhodamine 6G caused a severe damage of the cells, and rhodamine B significantly decreased the cell number; rhodamine 123 had no significant effect; rhodamine 116 significantly increased the cell number. Furthermore, rhodamine B decreased the number of both vascular endothelial cells from bovine aorta and vascular smooth muscle cells from murine aorta after a 72 h culture. It is concluded that rhodamine B inhibits the proliferation of human lip fibroblasts. This rhodamine B effect may be a warning sign for the dye toxicity.

Effect of lead on the glycosaminoglycans metabolism of bovine aortic endothelial cells in culture

We investigated the effect of lead nitrate (0.1, 1.0, 10 or 20 microM) on the metabolism of glycosaminoglycans (GAG) in confluent cultures of bovine aortic endothelial cells. It was found that lead at 10 and 20 microM significantly decreased the accumulation of [35S]sulfate-labeled GAG ([35S]GAG) both in the cell layer and the medium after a 24-h culture. A time course study showed that 10 microM lead decreased the accumulation of [3H]glucosamine-labeled GAG both in the cell layer and the medium after 24 h and longer. The release of [35S]GAG from the cell layer during the last 3 h of a 24 h culture was not changed by lead. The detachment of [3H]thymidine-labeled cells from the monolayer was unaffected by lead. It was shown that lead at 10 microM decreased both heparan sulfate and the other GAG in the cell layer; the former was more sensitive to lead treatment. Lead at 20 microM and below failed to increase the release of lactate dehydrogenase, suggesting that non-specific cell damage was not caused by lead. From these results, it was suggested that lead decreases endothelial cell heparan sulfate content through a decrease in the GAG production without a non-specific cell damage. Lead may be a risk factor of vascular disorders.

Sustained arterial injury and progression of atherosclerosis

In this paper the following findings were described: 1) Murine arteriosclerosis induced by immune challenge was ultrastructurally characterized by intimal monocyte-macrophage recruitment and minor endothelial alterations; 2) Atherosclerotic lesions of human coronary arteries exhibited frequently segmental or patchy neovascularization, probably representing a response to intimal injury as an example of repair process. Newly formed blood vessels in the intima were derived from both adventitial and luminal endothelial growth; 3) Angiogenesis in vitro was related to the activation of fibrinolytic system especially via the autocrine production of u-PA from endothelial cells, and this process was modulated by cytokines and TGF beta. These findings add more evidence for the hypothesis that the chronic inflammation-repair process plays an essential role in the initiation and progression of atherosclerosis.

Lessons in prevention of atherosclerosis learned from recent studies of Japanese youth

1) The incidence of myocardial infarction, as well as thrombosis, has been increasing recently in the consecutive autopsy cases over 40 years old in Kyushu University, but is still less frequent than those in the autopsy cases in Boston around 1960. Increased fat intake might play a significant role in the increasing frequency of myocardial infarction in Japanese. 2) In a nationwide cooperative study of atherosclerosis in young Japanese, atherosclerotic changes were observed to begin developing in childhood. Primary prevention of atherosclerosis should be initiated in the pediatric age group. We should pay more attention to subclinical atherosclerosis. Age, serum cholesterol, and blood pressure were significantly and positively correlated with SI and AI of aortas and coronary arteries. Serum cholesterol was more strongly correlated with the extent of fatty streaks than was mean blood pressure and vice versa with that of fibrous plaques. Atherosclerosis of cerebral arteries, however, showed a significant correlation only with the factor of mean blood pressure. Therefore the susceptibility to risk factors varies with the artery in the case of early lesions of atherosclerosis in young people. More attention should be paid to the fact that atherosclerosis is a multifactoral disease. 3) Deposition of fibrinogen in the intima might precede LDL deposition and possibly play a more important role than LDL in the development of atherosclerotic lesions in the cerebral arteries, especially in their early stage. 4) The proliferation of smooth muscle cells is stimulated by fibrin and later inhibited by FDP, as produced by fibrinolytic activity of smooth muscle cells. The metabolism of fibrin in the arterial wall may be of importance in the regulation of smooth muscle cell proliferation, and the coagulation-fibrinolysis system may play a significant role in atherosclerosis with the effect of other risk factors such as cholesterol and hypertension.

Heparin cofactor II inhibits thrombin-stimulated release of tissue plasminogen activator from cultured human endothelial cells in the presence of dermatan sulfate

To investigate the involvement of heparin cofactor II (HC II) in fibrinolytic system, endothelial cells from human umbilical vein were cultured in the presence of HC II or antithrombin III (AT III) combined with or without thrombin. Although AT III significantly inhibited thrombin-induced increase in tissue plasminogen activator antigen (t-PA:Ag) release, HC II did not exhibit such a suppressive effect. In contrast, in the presence of dermatan sulfate, HC II inhibited thrombin stimulation of t-PA:Ag release more strongly than AT III did. The release of plasminogen activator inhibitor-1 antigen (PAI-1:Ag) was also stimulated by thrombin; this stimulation was inhibited only by the combination of HC II and dermatan sulfate. Comparatively high concentrations of HC II significantly suppressed thrombin stimulation of t-PA:Ag and PAI-1:Ag release but did not cause an obvious change of both release in the absence of thrombin. Based on these results, it was suggested that HC II may inhibit an increase in fibrinolytic activity mediated by thrombin-stimulated endothelial cells in the liquid phase through a suppression of thrombin stimulation of t-PA:Ag release, when plasma is exposed to vascular smooth muscle cells or fibroblasts which synthesize a significant amount of dermatan sulfate.

Secretion of plasminogen activator and its inhibitor by glomerular epithelial cells

The effects of thrombin, interleukin-1 (IL-1), tumor necrosis factor (TNF) and gamma-interferon (gamma-IFN) on the release of plasminogen activator (PA) and inhibitor (PAI) were studied using cultivated human glomerular epithelial cells (GECs). Species of PAs and PAI secreted from the GECs were urokinase-type PA (u-PA) and tissue-type PA (t-PA), while the major species was a single chain u-PA in the amount of 28.6 +/- 2.34 ng/10(5) cells for 24 hours (N = 4, mean +/- SD), and PAI-1. The addition of increased concentrations of thrombin (0.1 to 31.6 U/ml) into confluent cultures enhanced the GECs to release u-PA, t-PA and PAI-1 in a dose- and time-dependent manner. The incubation of the GECs with 10 U/ml thrombin resulted in about a fourfold increase in the concentration of u-PA, threefold in t-PA and twofold in PAI-1. All thrombin effects, however, were suppressed by the simultaneous addition of cycloheximide, indicating that the enhancing effects of thrombin were due to an increase in the production of PAs and PAI-1, via protein synthesis. These thrombin effects appeared to be dependent upon the enzymatically active site of thrombin because DFP-thrombin had no effect. In the conditioned medium which was under continuous thrombin stimulation for 24 hours, no u-PA activity was detectable, even after the plasmin treatment, because a single chain u-PA was degraded by the thrombin. The stimulation of cultured GECs with thrombin only for the first three hours in 24 hour cultivation showed an apparent increase in the antigenic amount of u-PA. IL-1 enhanced the release of t-PA and PAI-1, and TNF did that of u-PA and t-PA, while gamma-IFN showed no significant effects. These findings indicate that the GECs participate in the regulation of extracapillary fibrinolysis in the glomerular microenvironment, as being modulated by thrombin and two cytokines, IL-1 and TNF.