Beurteilung der thrombolytischen Wirkung neuer Thrombolytika durch Bestimmung der spezifischen Fibrinspaltprodukte (D-Dimere)

Bei 52 Patienten, die sich wegen eines akuten Herzinfarktes der Thrombolysetherapie mit rt-PA (n = 26) oder Urokinase-präaktivierter Pro-Urokinase (n = 26) unterzogen, wurde die Freisetzung der D-Dimere mittels zweier unterschiedlicher, käuflicher ELISA-Methoden untersucht. Der Anstieg der D-Dimere wurde mit im Mittel + 3782 ± 4583 ìg/l in der Methode nach Stötzer et al. und mit + 5412 ± 6028 ìg/l in der Methode nach Koopmann et al. bestimmt. Die Werte beider Methoden waren mit r = 0,343 nur schwach miteinander korreliert (p <0,02). Eine Korrelation ähnlicher Qualität fand sich zwischen den nach Stötzer ermittelten D-Dimerspiegeln und den Fibrinogenspaltprodukten (FPA-enthaltende Fibrinogenfragmente, r = 0,374; p<0,01). Die nach Stötzer ermittelten Spiegel der D-Dimere korrelierten am besten mit der Konzentration aller (Fibrinogenplus Fibrin-)Spaltprodukte (r = 0,453; p <0,001). Bei der Methode nach Stötzer besteht somit eine erhebliche Kreuzreaktivität des monoklonalen Antikörpers mit den D-Monomeren. Nur wenn die Konzentration von D-Monomeren sicher vernachlässigbar klein ist, behält diese Methode ihren diagnostischen Stellenwert.

[Postoperative antithrombotic treatment in diabetic patients]

Diabetes mellitus patients after aorto-coronary bypass operation constitute a patient cohort at largely increased risk for secondary coronary events. Antiplatelet agents and antithrombotic agents are applied for secondary prevention. Up to now, secondary prevention has not been addressed specifically in the cohort of diabetic patients after bypass operation. Hence therapeutic recommendations are derived from the global cohort of CAD patients and based on risk assessment rather than on specific data. Since diabetic patients after myocardial infarction are at particularly high risk, combined therapy with clopidogrel and ASS may be considered even with restricted resources in the health system. Oral anticoagulation with coumadin constitutes an effective alternative to dual anti-platelet therapy. Under specific conditions (ventricular aneurysms, EF < 30%, or certain conditions in coronary anatomy) oral anticoagulants should be considered more liberally than currently.

[Coronary artery disease--relevance of total coronary revascularization on the incidence of malignant arrhythmias]

Myocardial ischemia induces redistribution of different ions (H(+), K(+), Na(+), Ca(++)) across the cardiomyocyte membrane, as well as the loss of intracellular ATP content. This results in changes in the electrical properties including shortening of the action potential, appearance of delayed afterpotentials, and a modified refractoriness of the cardiomyocyte. These changes may induce or support malignant cardiac arrhythmias. Supersensitivity of sympathetic denervated myocardium may further support the electrical instability of ischemic myocardium.Virtues of studies indicate that patients with coronary artery disease who develop complex arrhythmias during or after exercise bear a substantially increased risk for sudden cardiac death. Other studies report about arrhythmic stabilization and reduced mortality if patients with reversible myocardial ischemia receive complete revascularization. However, none of these studies is without methodological flaws. Due to the lack of methodologically sound studies in sufficiently large patient cohorts, the question whether complete coronary revascularisation improves the prognosis of patients with coronary artery disease and which strategy (medical, interventional, or surgical) warrants the best outcomes remains open.

Urokinase plasminogen activator augments cell proliferation and neointima formation in injured arteries via proteolytic mechanisms

Urokinase plasminogen activator (uPA) has been implicated in the healing responses of injured arteries, but the importance of its various properties that influence smooth muscle cell (SMC) proliferation and migration in vivo is unclear. We used three recombinant (r-) forms of uPA, which differ markedly in their proteolytic activities and abilities to bind to the uPA receptor (uPAR), to determine, which property most influences the healing responses of balloon catheter injured rat carotid arteries. After injury, uPA and uPAR expression increased markedly throughout the period when medial SMCs were rapidly proliferating and migrating to form the neointima. Perivascular application of uPA neutralizing antibodies immediately after injury attenuated the healing response, significantly reducing neointima size and neointimal SMC numbers. Perivascular application of r-uPAwt (wild type uPA) or r-uPA/GDF (r-uPA with multiple mutations in its growth factor-like domain) doubled the size of the neointima. Four days after injury these two uPAs nearly doubled neointimal and medial SMC numbers in the vessels, and induced greater reductions in lumen size than injury alone. Proteolytically inactive r-uPA/H/Q (containing glutamine rather than histidine-204 in its catalytic site) did not affect neointima or lumen size. Also, in contrast to the actions of proteolytically active uPAs, tissue plasminogen activator (tPA) did not affect the rate of neointima development. We conclude that uPA is an important factor regulating the healing responses of balloon catheter injured arteries, and its proteolytic property, which cannot be mimicked by tPA, greatly influences SMC proliferation and early neointima formation.

Ecarin clotting time but not aPTT correlates with PEG-hirudin plasma activity

BACKGROUND

Novel antithrombotic agents such as hirudin have shown promise in the therapy of acute coronary syndromes. PEG-hirudin (polyethyleneglycol conjugated hirudin) has been developed to provide a longer plasma half-life and more stable antithrombotic plasma levels. Privious trials indicated a narrow therapeutic window for hirudin and a number of aPTT (activated partial thromboplastin time)-monitored trials investigating hirudin in acute coronary syndromes had to be stopped because of intracranial bleeding complications.

OBJECTIVES

The present study evaluates the ecarin clotting time (ECT), a parameter based on the conversion of prothrombin by the snake venom enzyme ecarin, for the monitoring of PEG-hirudin therapy.

METHODS

Plasma from either healthy volunteers (n=20) or from patients (n=10) suffering from unstable angina pectoris (UAP) was spiked with increasing PEG-hirudin concentrations. In a prospective randomized clinical trial patients with UAP were treated with intravenous PEG-hirudin or heparin over 72 hours. Patients were randomized to the following treatment groups: (1) heparin control group, n=15; (2) PEG-hirudin low dose (0.1 mg/kg bolus, 0.01 mg/kg/h infusion), n=19; (3) intermediate dose (0.15 mg/kg and 0.015 mg/kg/h), n=17; 4) high-dose (0.2 mg/kg and 0.02 mg/kg/h), n=16. Spiked plasma samples and plasma from UAP patients treated with i.v. PEG-hirudin were analyzed for aPTT, ECT, and PEG-hirudin levels.

RESULTS

A linear correlation up to the highest therapeutic concentrations could be observed between PEG-hirudin plasma concentrations and the ECT. This was true for both plasma samples spiked with PEG-hirudin in vitro as well as for samples taken from patients treated with i.v. PEG-hirudin (correlation coefficient 0.9, respect.) In contrast the aPTT did not show a reliable linear correlation to PEG-hirudin concentrations.

CONCLUSION

Monitoring of PEG-hirudin therapy by ECT may help to avoid inadequate anticoagulation or overdosing. Thus, the safety and efficacy profile of PEG-hirudin therapy is likely to be enhanced by ECT monitoring.

Anticoagulation: the present and future

Thrombin is a central bioregulator of coagulation and is therefore a key target in the therapeutic prevention and treatment of thromboembolic disorders, including deep vein thrombosis and pulmonary embolism. The current mainstays of anticoagulation treatment are heparins, which are indirect thrombin inhibitors, and coumarins, such as warfarin, which modulate the synthesis of vitamin K-dependent proteins. Although efficacious and widely used, heparins and coumarins have limitations because their pharmacokinetics and anticoagulant effects are unpredictable, with the risk of bleeding and other complications resulting in the need for close monitoring with their use. Low-molecular-weight heparins (LMWHs) provide a more predictable anticoagulant response, but their use is limited by the need for subcutaneous administration. In addition, discontinuation of heparin treatment can result in a thrombotic rebound due to the inability of these compounds to inhibit clot-bound thrombin. Direct thrombin inhibitors (DTI) are able to target both free and clot-bound thrombin. The first to be used was hirudin, but DTIs with lower molecular weights, such as DuP 714, PPACK, and efegatran, have subsequently been developed, and these agents are better able to inhibit clot-bound thrombin and the thrombotic processes that take place at sites of arterial damage. Such compounds inhibit thrombin by covalently binding to it, but this can result in toxicity and nonspecific binding. The development of reversible noncovalent DTIs, such as inogatran and melagatran, has resulted in safer, more specific and predictable anticoagulant treatment. Oral DTIs, such as ximelagatran, are set to provide a further breakthrough in the prophylaxis and treatment of thrombosis.

[Significance of the uPA/uPAR system for development of arteriosclerosis and restenosis]

Arteriosclerosis and the development of restenosis still remain a significant clinical problem. Migration of vascular smooth muscle cells from the media to the intima and cell proliferation are the hallmarks of the underlying pathomechanisms. Cell migration requires chemotaxis, phenotypic changes of cells, cell adhesive and de-adhesive events and the coordinated remodeling of the extracellular matrix. One of the phenotypic changes induced in migrating cells is the increased expression of urokinase plasminogen activator (uPA) and of its specific receptor uPAR. They are polarized to the leading edge of migrating cells. Both uPA and uPAR are key mediators of extracellular proteolysis. They participate in extracellular matrix remodeling, activate cells and enable them to migrate and invade into different tissue layers. UPA/uPAR are multifunctional proteins influencing a great variety of signal transduction pathways ultimately culminating in the regulation of cell migration and proliferation. In addition to time- and space-confined proteolysis this powerful system can mediate chemotaxis, cell adhesion and gene expression, partly by interacting in concert with integrins, G proteins, or with yet unidentified coreceptors or adapter molecules. Interaction with the uPA/uPAR system or components of its specific signal transduction pathways may serve as a guide for the development of effective therapeutic strategies to prevent arteriosclerosis and restenosis after percutaneous arterial angioplastic interventions.

Direkte Thrombinantagonisten

BACKGROUND

Inhibiting thrombin as a key enzyme of the coagulation cascade is therapeutically useful in thromboembolic diseases. In coronary thrombosis, direct thrombin inhibitors promise to be useful for an efficacious therapy. Hirudin and recombinant or synthetic mimetics like hirulog, argatroban and melagatran have proven their efficacy in clinical studies.

CONCLUSION

Therapy with direct thrombin inhibitors such as hirudin and analogous substances reduces coronary events. Moreover, the agents are useful for therapy of thromboembolic diseases, especially in the case of heparin induced thrombocytopenia type II.

Niedermolekulare Heparine in der Kardiologie

Bei thromboembolischen Herzerkrankungen hat sich unfraktioniertes Heparin in hohen Dosen als außerordentlich wirksam erwiesen. Bei der subkutanen Verabreichung muss jedoch mit einer unsicheren Resorption aus dem subkutanen Fettgewebe gerechnet werden, weshalb im Allgemeinen eine intravenöse Heparin-Dauerinfusion bevorzugt wird. Das ungünstige pharmakologische Profil der Substanz und die hohen inter- und intraindividuellen Schwankungen der Dosis-Wirkungs-Beziehung ziehen jedoch bei intravenöser Verabreichung die Notwendigkeit engmaschiger Laborkontrollen nach sich (Übersicht bei [1, 2]).

Die Frühmobilisation und die Erhaltung der Mobilität kardial erkrankter Patienten nehmen heute in der Therapie einen dominanten Platz ein. Die Notwendigkeit der intravenösen Verabreichung ebenso wie die Komplexität der Therapie stehen bei den unfraktionierten Heparinen der Frühmobilisation und der ambulanten Fortführung der Behandlung entscheidend entgegen. Mit den fraktionierten (niedermolekularen) Heparinen steht nunmehr eine Heparinklasse zur Verfügung, die neben der verlässlichen Resorption aus dem subkutanen Fettgewebe auch eine wesentlich besser vorhersagbare Dosis-Wirkungs-Beziehung aufweist (Übersicht bei [1, 2]). Da diese Heparine darüber hinaus bei der primären Anwendung sehr viel seltener mit der Ausbildung einer lebensgefährlichen HIT (Heparin-induzierte Thrombozytopenie) assoziiert sind (3), wird ihr routinemäßiger Einsatz auch bei kardiologisch erkrankten Patienten immer häufiger erwogen. Das instabile Koronarsyndrom (instabile Angina pectoris und nicht-transmuraler Herzinfarkt) nimmt diesbezüglich eine Vorreiterrolle in der Kardiologie ein.

Urokinase stimulates human vascular smooth muscle cell migration via a phosphatidylinositol 3-kinase-Tyk2 interaction

Janus kinases Jak1 and Tyk2 play an important role in urokinase-type plasminogen activator (uPA)-dependent signaling. We have recently demonstrated that both kinases are associated with the uPA receptor (uPAR) and mediate uPA-induced activation of signal transducers and activators of transcription (Stat1, Stat2, and Stat4) in human vascular smooth muscle cells (VSMC). Janus kinases are not only required for Stat activation but may also interfere with other intracellular signaling pathways. Here we report that in VSMC, Tyk2 interacts with a downstream signaling cascade involving phosphatidylinositol 3-kinase (PI3-K). We demonstrate that uPA induces PI3-K activation, which is abolished in VSMC expressing the dominant negative form of Tyk2. The regulatory subunit p85 of PI3-K co-immunoprecipitates with Tyk2 but not with Jak1, Jak2, or Jak3, and uPA stimulation increases the PI3-K activity in Tyk2 immunoprecipitates. Tyk2 directly binds to either of the two Src homology 2(SH2)p85 domains in a uPA-dependent fashion. We provide evidence that the Tyk2-mediated PI3-K activation in response to uPA is required for VSMC migration. Thus, two unrelated structurally distinct specific inhibitors of PI3-K, wortmannin and LY294002, prevent VSMC migration induced by uPA. No migratory effect of uPA was observed in VSMC expressing the dominant negative form of Tyk2. Our results underscore the versatile function of Tyk2 in uPA-related intracellular signaling and indicate that PI3-K plays a selective role in the regulation of VSMC migration.

[Recommendations of the International Cardiology Forum (ICF) 1998 on revision of the current guidelines for the diagnosis and treatment of unstable angina pectoris and nontransmural myocardial infarct]

Rapid progress in the understanding and treatment of unstable angina and acute coronary syndrome are prompting occasional revisions to current treatment guidelines. The recommendations contained in this paper are based on the consensus reached during discussions at the 'International Cardiology Forum' in September 1998. Consensus was reached on significant major points, although some aspects remain controversial. A substantial body of data accumulated in a host of studies justify changes to current treatment habits.

AT(1) receptor agonistic antibodies from preeclamptic patients cause vascular cells to express tissue factor

BACKGROUND

We recently described autoantibodies (angiotensin-1 receptor autoantibodies, AT(1)-AA) directed at the AT(1) receptor in the serum of preeclamptic patients, whose placentas are commonly infarcted and express tissue factor (TF). Mechanisms of how AT(1)-AA might contribute to preeclampsia are unknown. We tested the hypothesis that AT(1)-AA cause vascular smooth muscle cells (VSMC) to express TF.

METHODS AND RESULTS

IgG from preeclamptic patients containing AT(1)-AA was purified with anti-human IgG columns. AT(1)-AA were separated from the IgG by ammonium sulfate precipitation. We transfected Chinese hamster ovary cells overexpressing the AT(1) receptor with TF promoter constructs coupled to a luciferase reporter gene. VSMC were obtained from human coronary arteries. Extracellular signal-related kinase activation was detected by an in-gel kinase assay. AP-1 activation was determined by electromobility shift assay. TF was measured by ELISA and detected by immunohistochemistry. Placentas from preeclamptic women stained strongly for TF, whereas control placentas showed far less staining. We proved AT(1)-AA specificity by coimmunoprecipitating the AT(1) receptor with AT(1)-AA but not with nonspecific IgG. Angiotensin (Ang) II and AT(1)-AA both activated extracellular signal-related kinase, AP-1, and the TF promoter transfected VSMC and Chinese hamster ovary cells, but only when the AP-1 binding site was present. We then demonstrated TF expression in VSMC exposed to either Ang II or AT(1)-AA. All these effects were blocked by losartan. Nonspecific IgG or IgG from nonpreeclamptic pregnant women had a negligible effect.

CONCLUSIONS

We conclude that AT(1)-AA and Ang II both stimulate the AT(1) receptor and initiate a signaling cascade resulting in TF expression. These results show an action of AT(1)-AA on human cells that could contribute to the pathogenesis of preeclampsia.

Urokinase-induced mitogenesis is mediated by casein kinase 2 and nucleolin

BACKGROUND

Urokinase (uPA) and the urokinase receptor (uPAR) form a multifunctional system capable of concurrently regulating pericellular proteolysis, cell-surface adhesion, and mitogenesis. The role of uPA and uPAR in directed proteolysis is well established and its function in cellular adhesiveness has recently been clarified by numerous studies. The molecular mechanisms underlying the mitogenic effects of uPA and uPAR are still unclear, however.

RESULTS

We identified mechanisms that might participate in uPA-related mitogenesis in human vascular smooth muscle cells and demonstrated that uPA induces activation of a unique signaling complex. This complex contains uPAR and two additional proteins, nucleolin and casein kinase 2, which are implicated in cell proliferation. Both proteins were isolated by affinity chromatography on uPA-conjugated cyanogen-bromide-activated Sepharose 4B and were identified using nano-electrospray mass spectrometry and immunoblotting. We used laser scanning and immunoelectron microscopy studies to further demonstrate that nucleolin and casein kinase 2 are located on the cell surface where they colocalize with the uPAR. Moreover, the proteins were co-internalized into the cell as an entire complex. Immunoprecipitation experiments in combination with an in vitro kinase assay demonstrated a specific association of uPAR with nucleolin and casein kinase 2 and revealed a uPA-induced activation of casein kinase 2, which presumably led to phosphorylation of nucleolin. Blockade of nucleolin and casein kinase 2 with specific modulators led to the inhibition of uPA-induced cell proliferation.

CONCLUSIONS

We conclude that in human vascular smooth muscle cells, uPA induces the formation and activation of a newly identified signaling complex comprising uPAR, nucleolin, and casein kinase 2, that is responsible for the uPA-related mitogenic response. The complex is not a unique feature of vascular smooth muscle cells, as it was also found in other uPAR-expressing cell types.

Urokinase activates calcium-dependent potassium channels in U937 cells via calcium release from intracellular stores

The urokinase receptor (uPAR) is highly expressed in the human promyelocytic cell line U937 and contributes to transmembrane signalling. However, the signalling mechanisms are poorly understood. We used the patch-clamp technique to demonstrate that urokinase (uPA) binds to uPAR and thereby stimulates Ca(2+)-activated K+ channels in U937 cells. uPA transiently increased K+ currents within 30 s. The K+ currents were pertussis toxin-sensitive and were also observed in Ca(2+)-free solution. However, when cells were dialysed with EGTA, uPA did not affect K+ currents. The intracellular Ca2+ response to uPA was independent of extracellular Ca2+, was pertussis toxin-sensitive, and was blocked by both thapsigargin and the phospholipase C inhibitor U-73122. The uPA-induced increase in intracellular Ca2+ was independent of uPA proteolytic activity. Furthermore, uPA initiated a rapid formation of inositol 1,4, 5-trisphosphate [Ins(1,4,5)P3]. The amino-terminal uPA fragment and uPA inactivated with diisopropyl fluorophosphate or with inhibitory antibody, elicited the same Ca2+ signal. On the other hand, Ca2+ signalling required the intact uPAR because the effects were abrogated by PtdIns-specific phospholipase C, which removes the uPAR from the cell surface. The prevention of glycosyl phosphatidylinositol moiety synthesis and interference with uPAR anchoring to the cell surface using mannosamine also abolished Ca2+ signals. Taken together, our findings indicate that uPA binds to uPAR and stimulates the production of Ins(1,4,5)P3 via a G-protein- and phospholipase C-dependent mechanism. Ins(1,4,5)P3 in turn liberates Ca2+ from intracellular stores, which leads to the stimulation of Ca(2+)-activated K+ channels.

Chlamydia pneumoniae infection of vascular smooth muscle and endothelial cells activates NF-kappaB and induces tissue factor and PAI-1 expression: a potential link to accelerated arteriosclerosis

BACKGROUND

Recent reports link C. pneumoniae infection of arteriosclerotic lesions to the precipitation of acute coronary syndromes, which also feature tissue factor and plasminogen activator inhibitor 1 (PAI-1) overexpression. We investigated whether or not C. pneumoniae can induce thrombogenicity by upregulation of procoagulant proteins.

METHODS AND RESULTS

Human vascular endothelial and smooth muscle cells were infected with a strain of C. pneumoniae isolated from an arteriosclerotic coronary artery. Tissue factor, PAI-1, and interleukin-6 expression was increased in infected cells. Concomitantly, NF-kappaB was activated and IkappaBalpha degraded. p50/p65 heterodimers were identified as the components responsible for the NF-kappaB activity.

CONCLUSIONS

These data provide evidence that C. pneumoniae infection can induce procoagulant protein and proinflammatory cytokine expression. This cellular response is accompanied by activation of NF-kappaB. Our results demonstrate how C. pneumoniae infection may initiate acute coronary syndromes.

Ventricular remodeling after acute myocardial infarction

The term ventricular remodeling has been coined to describe the geometrical changes in size and shape of the left ventricle occurring after large myocardial infarcts. We do not exactly know what initiates this process. Slipping of myofilaments following destruction of connective tissue--probably due to metalloproteinase activation--could be the initial event. As a consequence, wall stress is increased triggering deleterious adaptation processes, such as: - intracardiac angiotensin II generation; - cardiac endothelin formation and release; - pro-apoptotic signals for cardiomyocytes; - hypertrophic signals for fibroblasts and cardiomyocytes. This cascade of events is not only observed in the process of remodeling following myocardial infarction but is also operating during the progression of heart failure. Therapeutic principles therefore are similar in both conditions: - reduction of wall stress (pharmacological or mechanical unloading of the heart); - blockade of angiotensin II generation or of AT1-receptors (ACE-inhibitors or AT1 antagonists); - blockade of endothelin receptors (ET(A)-blockers); - blockade of adrenergic receptors (preferably beta1-adrenergic receptor blockers). Better understanding of the molecular mechanisms of the remodeling process already has fueled the search for new therapeutic interventions (such as endothelin receptor blockers, aldosterone antagonists and growth hormone application). Continuous research in this field may be especially rewarding if we will succeed in identifying the very first step in the cascade.

Urokinase induces activation and formation of Stat4 and Stat1-Stat2 complexes in human vascular smooth muscle cells

Urokinase-type plasminogen activator (uPA) and its specific receptor (uPAR) act in concert to stimulate cytoplasmic signaling machinery and transcription factors responsible for cell migration and proliferation. Recently we demonstrated that uPA activates the Janus kinase/signal transducers and activators of transcription (Stat1) signaling in human vascular smooth muscle and endothelial cells. However, the important question whether other transcription factors of the Stat family, in addition to Stat1, are involved in the uPAR-related signaling has not been addressed. In this study, we demonstrate that Stat4 and Stat2, but not Stat3, Stat5, or Stat6, are rapidly activated in response to uPA. We demonstrate further that Stat4 and Stat2 rapidly and transiently translocate to the cell nucleus where they bind specifically to the regulatory DNA elements. Analysis of Stat complexes formed in response to uPA revealed a Stat2-Stat1 heterodimer, which lacks p48, a DNA-binding protein known to combine with Stat1-Stat2. This new uPA-induced Stat2-Stat1 heterodimer binds to GAS (the interferon-gamma activation site) distinct from the interferon-stimulated response element to which the p48 protein containing complexes generally bind. We conclude that uPA activates a specific and unusual subset of latent cytoplasmic transcription factors in human vascular smooth muscle cells that suggests a critical role of uPA in these cells.

Urokinase activates the Jak/Stat signal transduction pathway in human vascular endothelial cells

Endothelial cells demonstrate high urokinase expression and upregulation of urokinase receptors in response to vascular injury. Urokinase receptor binding facilitates endothelial cell migration into an arterial wound; however, the signaling cascade induced by the urokinase receptor in this cell type is incompletely understood. Because the Janus kinase (Jak)/signal transducer and activator of transcription (Stat) pathway seems to be important for vessel function, we investigated the hypothesis that urokinase receptor binding activates Jak/Stat signaling in human vascular endothelial cells. Incubation of endothelial cells with urokinase-type plasminogen activator (uPA,1 nmol/L) induced a rapid and pronounced increase in tyrosine phosphorylation of several proteins with a molecular weight between 80 to 90 and 130 to 140 kDa. The same pattern of tyrosine phosphorylation was found after treatment with 1 nmol/L ATF, the urokinase amino-terminal fragment, which is devoid of proteolytic activity but still binds to the urokinase receptor. Using coimmunoprecipitation techniques, we demonstrated that the activated urokinase receptor is associated with 2 cytoplasmic tyrosine kinases of the Jak family, viz, Jak1 and Tyk2. uPA and ATF induced a time-dependent activation of both kinases, as shown by immunoprecipitation and Western blot analysis. Using electrophoretic mobility shift and supershift assays, we then demonstrated that Stat1 is rapidly activated in endothelial cells in response to uPA and ATF. Furthermore, Stat1 specifically binds to the regulatory elements interferon-gamma activation site/interferon-stimulated response element. The uPA-induced, time-dependent translocation of Stat1 to cell nuclei was confirmed by confocal microscopy study and immunoblotting of nuclear extracts with an anti-Stat1 antibody. This study provides evidence for a novel signaling pathway for uPA in human vascular endothelial cells. Direct activation of the Jak/Stat system via the uPA-receptor complex may be an important mechanism for endothelial cell migration and/or proliferation during angiogenesis and after vascular injury.

Ventricular Remodeling after Acute Myocardial Infarction

The term ventricular remodeling has been coined to describe the geometrical changes in size and shape of the left ventricle occurring after large myocardial infarcts.

We do not exactly know what initiates this process. Slipping of myofilaments following destruction of connective tissue – probably due to metalloproteinase activation – could be the initial event.

As a consequence, wall stress is increased triggering deleterious adaptation processes, such as

– intracardiac angiotensin II generation

– cardiac endothelin formation and release

– pro-apoptotic signals for cardiomyocytes

– hypertrophic signals for fibroblasts and cardiomyocytes

This cascade of events is not only observed in the process of remodeling following myocardial infarction but is also operating during the progression of heart failure.

Therapeutic principles therefore are similar in both conditions:

– reduction of wall stress (pharmacological or mechanical unloading of the heart)

– blockade of angiotensin II generation or of AT1-receptors (ACEinhibitors or AT1 antagonists)

– blockade of endothelin receptors (ETA-blockers)

– blockade of adrenergic receptors (preferably β1-adrenergic receptor blockers).

Better understanding of the molecular mechanisms of the remodeling process already has fueled the search for new therapeutic interventions (such as endothelin receptor blockers, aldosterone antagonists and growth hormone application). Continuous research in this field may be especially rewarding if we will succeed in identifying the very first step in the cascade.

The Jak/Stat pathway and urokinase receptor signaling in human aortic vascular smooth muscle cells

The binding of urokinase plasminogen activator (uPA) to its specific receptor (uPAR) facilitates migration of vascular smooth muscle cells (VSMC). However, the signaling cascade utilized by the urokinase receptor is only incompletely understood. We investigated intracellular uPA/uPAR signaling in human aortic VSMC from the cell membrane to the nucleus. uPA binding to VSMC induced a rapid and pronounced increase in tyrosine phosphorylation of several proteins with molecular masses of 53-60, 85-90, and 130-140 kDa. By using co-immunoprecipitation techniques and in vitro kinase assays, the uPAR-associated proteins were identified as Janus (Jak) and Src non-receptor protein-tyrosine kinases (PTK) Jak1, Tyk2, and p59(fyn), p53/56(lyn), p53/59(hck), and p55(fgr). Furthermore, uPA induced a time-dependent reversible translocation of the Stat1 (signal transducer and activator of transcription) protein to the VSMC nuclei, as shown by confocal microscopy studies. Using an electrophoretic mobility shift assay, we then demonstrated that Stat1 is rapidly activated in response to stimulation with uPA and specifically binds to the DNA regulatory elements GAS (interferon-gamma activation site) and ISRE (interferon-stimulated response element). Mobility supershift experiments confirmed DNA-protein complexes containing Stat1 protein. Migration experiments with double immunofluorescence staining revealed polarization of uPAR, and colocalization with Jak1 and Tyk2 to the leading edge of the migrating cells. Under the same conditions, Jak2, Jak3, and the Src-PTKs remained randomly distributed over the entire body of the cells. Our studies therefore suggest that, in VSMC, the uPAR-signaling complex utilizes at least two different mechanisms, a direct signaling pathway utilizing the Jak/Stat cascade and a second signal transduction mechanism via Src-like protein-tyrosine kinases. uPA-induced signaling via Jak/Stat is most likely involved in the regulation of cell migration, while the functional purpose of the uPA-associated Src-PTK activation remains to be elucidated.

Sixty-minute alteplase protocol: a new accelerated recombinant tissue-type plasminogen activator regimen for thrombolysis in acute myocardial infarction

OBJECTIVES

Our aim was to design and evaluate a new and easily administered recombinant tissue-type plasminogen activator (rt-PA) regimen for thrombolysis in acute myocardial infarction (AMI) based on established pharmacokinetic data that improve the reperfusion success rate.

BACKGROUND

Rapid restoration of Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow is a primary predictor of mortality after thrombolysis in AMI. However, TIMI grade 3 patency rates 90 min into thrombolysis of only 50% to 60% indicate an obvious need for improved thrombolytic regimens.

METHODS

Pharmacokinetic simulations were performed to design a new rt-PA regimen. We aimed for a plateau tissue-type plasminogen activator (t-PA) plasma level similar to that of the first plateau of the Neuhaus regimen. These aims were achieved with a 20-mg rt-PA intravenous (i.v.) bolus followed by an 80-mg i.v. infusion over 60 min (regimen A). This regimen was tested in a consecutive comparative trial in 80 patients versus 2.25 10(6) IU of streptokinase/60 min (B), and 70 mg (C) or 100 mg (D) of rt-PA over 90 min. Subsequently, a confirmation trial of regimen A in 254 consecutive patients was performed with angiographic assessment by independent investigators of patency at 90 min.

RESULTS

The comparative phase of the trial yielded, respectively, TIMI grade 3 and total patency (TIMI grades 2 and 3) of 80% and 85% (regimen A), 35% and 50% (B), 50% and 55% (C) and 60% and 70% (D). In the confirmation phase of the trial, regimen A yielded 81.1% TIMI grade 3 and 87.0% total patency. At follow-up angiography 7 (4.1%) of 169 vessels had reoccluded. In-hospital mortality rate was 1.2%. Nadir levels of fibrinogen, plasminogen and alpha2-antiplasmin were 3.6 +/- 0.8 mg/ml, 60 +/- 21% and 42 +/- 16%, respectively (mean +/- SD). Fifty-seven patients (22.4%) suffered from bleeding; 3.5% needed blood transfusions.

CONCLUSIONS

The 60-min alteplase thrombolysis in AMI protocol achieved a TIMI grade 3 patency rate of 81.1% at 90 min with no indication of an increased bleeding hazard; it was associated with a 1.2% overall mortality rate. These results are substantially better than those reported from all currently utilized regimens. Head to head comparison with established thrombolytic regimens in a large-scale randomized trial is warranted.

Stent implantation in patients with superior vena cava syndrome

OBJECTIVE

The purpose of this study was to determine the feasibility of using Wallstent implantation to treat superior vena cava syndrome due to malignant tumors.

SUBJECTS AND METHODS

Digital subtraction angiography showed obstruction of the superior vena cava in 13 patients who then underwent transluminal dilatation and Wallstent implantation. The patients were treated with IV heparin and monitored in the emergency department. Thereafter, they were treated with a platelet inhibitor for 4 weeks.

RESULTS

Because their signs and symptoms improved, patients were able to resume radiation therapy, chemotherapy, or both. One patient died of cardiac arrhythmia 1 day after stent placement. Although eight patients have subsequently died of their bronchial or thyroid gland tumors, superior vena cava syndrome did not recur in any patient.

CONCLUSION

Percutaneous implantation of Wallstent endoprostheses provides excellent palliation for superior vena cava syndrome.

[Stents: new studies--new trends]

The increasing frequency of stent implantation into coronary arteries is based mainly on assumptions. One of these assumptions is that stents may prevent restenosis. Stents can prevent restenosis as has been shown in two randomized studies (Stress I and Benestent I), but only in large (> 3.0 mm) vessels with short denovo lesions. Despite the very tight selection of patients suitable for stent implantation in these two studies, the advantage for stents remained small (about 10% less restenosis) and appeared to decrease with time following intervention. There is increasing concern about the extension of stenting in an "unrestricted strategy". This concern was expressed in the ACC Expert Consensus Document which was published recently (JACC 28, No 3, September 1996: 782-794). Based on lack of data for most of the presently used stent indications the expert group recommended a more selective strategy for the implantation of stents into coronary arteries.

-Anticoagulant drugs-

In todays medicine, anticoagulant drugs like heparin and coumadin derivatives have become indispensable for the treatment of thrombo-embolic diseases. Heparin, consisting of long poly-sulfated polysaccharide chains of variable length and sequences is mostly derived from porcine mucosa. Its bioavailability by other than the parenteral way of administration is almost negligible. Therefore, with only few exceptions, it is almost exclusively applied in hospitalized patients (short-term therapy) or to bridge 2 phases of treatment with oral anticoagulant drugs. Today, besides the conventional high-molecular weight heparins, new fractionated heparins are gaining more and more attention. They offer the advantage of a more reliable resorption from the subcutaneous tissue and thus warrant reliable plasma levels. In many recent randomized trials of deep vein thrombosis and pulmonary embolism, those fractionated heparins have proven to successfully substitute for intravenously applied, aPTT-controlled unfractionated heparin. It remains however open, whether this also translates into the prevention of arterial thrombo-embolic diseases. Heparin may not pass through the placental barrier nor into the milk and is regarded non-teratogenic. Therefore, it may be regarded the ideal anticoagulant for pregnant women and lactating mothers. Those women, however, still carry the heparin-associated risk of bleeding and osteoporosis. In comparison: Coumadin derivatives interfere with the carboxylation of the clotting factors II, VII, IX, and X as well as proteins C and S. By inhibiting the synthesis of these proteins they shift the haemostatic balance to a lower level. In addition, they are almost completely bioavailable by the enteral pathway. They are, therefore, regarded the drugs of choice for long-term anticoagulant therapy in patients at particular thromboembolic risk. For their therapeutic range, being extremely narrow, meticulous drug monitoring by repeated INR-measurements as well as a reliable compliance of the patient to drug intake and dietary restrictions are mandatory to exclude phases with over- or under-anticoagulation. Above all, coumadin therapy is characterized by numerous drug interactions. Thus, whenever the basal medication is changed, for whatever reason, more intense care must be laid to drug monitoring, and the intervals for INR determinations must transiently be shortened. Coumadin derivatives do pass through the placental barrier and in minor amounts also into the milk of breast feeding mothers. Furthermore, they are highly teratogenic. If taken during pregnancy, malformations of the central nervous system are reported to occur in some 10% to 30% of the infants. Thus during pregnancy and in the lactation period, coumadin therapy should be avoided. Bleeding episodes of different severity are the most frequent adverse effects of anticoagulant therapy, no matter whether heparin or coumadin is given. There is a direct relation between the intensity of anticoagulant therapy and the frequency of bleeds. Luckily, most bleeding episodes do not create major therapeutic problems. In case of severe bleeds, however, the anticoagulant therapy must immediately be suspended. In case of coumadin therapy the immediate administration of 4 packs of PPSB (prothrombin-complex-concentrates) or FFP (fresh-frozen-plasma) with concomitant low doses of heparin is additionally advised. Allopecia diffusa, urticartia and allergic reactions are known side effects of anticoagulant therapy. Patients on long-term heparin may also suffer from severe osteoporosis. On the other hand, heparin treatment raises the hazzards of a HAT-Syndrome (heparin-associated thrombocytopenia) (estimated frequency 0.01% to 0.1% of treated patients), giving rise to severe and life-threatening thrombo-embolic side effects predominantly in the arterial tree. In these cases, heparin must be suspended despite those severe thrombo-embolic episodes.

Thrombolysis in thromboembolic diseases

Thrombolysis in many manifestations of thromboembolic disease offers a valuable alternative to surgery. However, as thrombolysis is always associated with a bleeding hazard (though low) one should always weigh the risks against the expected benefits when the decision for or against this therapeutic option is made. Furthermore, in selecting the appropriate thrombolytic agent, one should be led by the urgency of reperfusion to maintain organ function. If one decides on an aggressive, high-dose, brief-duration regimen, reperfusion may be achieved more rapidly but may be incomplete in the majority of cases. On the other hand, by selecting an intermediate- or long-duration, low-dose regimen, reperfusion may happen too late to improve the patient's prognosis. Above all, one should keep in mind that the hazard of serious bleeding constantly increases with duration of thrombolysis. No matter which strategy is regarded as the best to resolve a clot in a particular patient with a particular type of thromboembolic disease, thrombolysis should be accompanied by high doses of i.v. heparin. Finally, if bleeding occurs in spite of all precautions taken, the new generation of fibrin-specific thrombolytic agents offers the advantage of short half-lives. In addition--in contrast to streptokinase--the hemostatic defect that they cause may be rapidly reversed by the infusion of antagonist drugs such as aprotinin, tranexamic acid, or epsilon-aminocaproic acid. This adds to the clinical safety profile of these thrombolytic agents.

Medical compared with surgical treatment for massive pulmonary embolism

We compared embolectomy (when available) with thrombolysis in patients with shock and massive pulmonary embolism. 13 patients were operated on, 10 (77%) of whom survived. The inferior vena cava was routinely clipped. The 24 medically treated patients were given alteplase until systemic and pulmonary artery pressures stabilised and heparin thereafter; 16 (67%) survived. Major haemorrhage occurred in 28% of medically treated patients, but was not fatal. 1 patient had a small cerebral haemorrhage that resolved without drainage. One-fifth of the medical group had a re-embolism, which suggests that temporary caval umbrellas are indicated in medically treated patients. Thrombolysis may provide a life-saving option and a randomised trial is warranted.

[Value of laboratory diagnosis in thrombolytic therapy]

Today, profound insight into the clotting and fibrinolytic systems during therapeutic thrombolysis is offered by a variety of laboratory assays. While the purpose of scientific investigations is to increase the knowledge on changes imposed by the mechanism of thrombolysis, the rationale for performing coagulation assays during thrombolytic therapy is to increase the safety of treatment. To make laboratory monitoring of thrombolytic therapy most effective, the main issues which should be solved should be defined. The main reasons for performing coagulation assays during and after thrombolytic therapy are: 1. To monitor the adjunctive anticoagulant therapy. 2. To detect potential bleeding hazards early, and 3. in case bleeding complications occur, to help to optimise of the therapeutic strategies to avoid excessive diagnostics. Most of the methods affording an insight into coagulation and fibrinolysis are not very helpful in terms of improved therapeutic safety. Too frequent repetition of assays is likewise superfluous. In our opinion, clinical routine monitoring should consist of red blood cell count, aPTT, and fibrinogen according to Clauss' method which should be repeated during the first 48 hours after initiation of therapy at 8- to 12-hour intervals. It must be mentioned in this respect that fibrinogen according to Clauss' method during thrombolytic therapy must be regarded an assay to estimate the global coagulation potential of the blood rather than to quantify fibrinogen levels. In our opinion, it is this that makes the Clauss' method superior to other methods of fibrinogen determination.

[Thrombolytic therapy in the past, present and future]

During the last decade, thrombolysis has developed in a unique and unprecedented way from an outsider method to a well-established standard treatment in acute myocardial infarction. Since the use of thrombolytic techniques in other entities of thromboembolic disease has been prompted by this success. As an introduction into this intriguing and inspiring field in clinical science, the present paper tries to summarise briefly the development of thrombolysis since 1933 when "fibrinolysin" was discovered in the culture medium of beta-haemolysing streptococci, as well as the presence and future of thrombolytic therapy.

[Undesirable side effects in thrombolytic therapy]

Even with the new fibrin-specific plasminogen activators thrombolytic therapy remains burdened with numerous side effects, some of them being severe or even life threatening, therapists being horrified if in rare cases the patient dies from severe haemorrhage subsequent to thrombolysis. The incidence and severity of bleeding increase with increasing aggressiveness of the therapeutic regimen and with increasing time during which the thrombolytic state is maintained. Furthermore, side effects related either to the plasminogen activator used (allergic reactions and systemic fibrinogen breakdown e.g.) or related to the underlying disease (pulmonary embolism and reperfusion arrhythmias e.g.) have to be considered. In order not to let thrombolysis become a double-edged sword, the risks of thrombolytic therapy should carefully be weighted against the benefits before thrombolysis is commenced.

[The value of late thrombolytic perfusion in acute myocardial infarct]

Contradicting previous views that reperfusion therapy in acute myocardial infarction has to be restricted to the first 4 to 6 h, the paradigm of thrombolysis in acute myocardial infarction has to be expanded to 12 h, since the results of the LATE study have been published. While early thrombolysis (up to 90 min) aims towards myocardial salvage, the benefit of late reperfusion seems to depend on an improved myocardial remodeling and on rhythmic stabilization (open artery hypothesis). Today the value of late reperfusion therapy can be regarded as proven in a clinical setting, the mechanisms of late reperfusion therapy, however, still remain to be settled.

Multicenter dose-finding trial for thrombolysis with urokinase preactivated pro-urokinase (TCL 598) in acute myocardial infarction. German Preactivated Pro-Urokinase Study Group

In a multicenter dose-finding study, the thrombolytic potency of urokinase preactivated pro-urokinase was evaluated. Sixty-two patients were randomly assigned to receive 250,000 U of urokinase plus either 4.5 mega U (group I: n = 33) or 6.5 mega U (group II: n = 29) of pro-urokinase. Patency rates were 36.4% (20.4-54.9%) vs. 54.5% (36.3-71.9%) (n = 27) at 60 minutes and 55.6% (32.5-70.6%) vs. 62.1% (42.3-79.3%) at 90 min into thrombolysis (n.s.). In a third group of 12 patients treated with 500,000 U of urokinase plus 6.5 mega U of pro-urokinase patency was achieved in 33.3% (9.9-65.1%) and 41.7% (15.2-72.3%) at 60 and 90 min, respectively. Patency rates at 24 hr follow-up angiography (n = 35) were 78.6% (49.2-95.3%), 85.7% (57.2-98.2%), and 85.7% (42.1-99.6%). Coagulation analysis in 37 patients revealed similar alterations in the three treatment groups with minor decreases in fibrinogen levels, moderate drops in plasminogen and alpha-2-antiplasmin levels, and moderate increases in the concentrations of the total fibrinogen/fibrin degradation products, the differences between the groups not being significant. Bleeding complications were observed in 12.9%, 13.8%, and 25% of patients in groups I, II, and III, respectively, mainly related to catheter sites. Hence, the safety profile of urokinase preactivated pro-urokinase seems comparable to other thrombolytic regimens. Reopening of occluded coronary arteries, however, is achieved relatively slowly. Thus, in its use for thrombolysis in myocardial infarction, urokinase preactivated pro-urokinase does not seem to offer superior advantages.

Intravenöse Thrombolysetherapie des akuten Herzinfarktes

Die intravenöse Thrombolysetherapie kann, insbesondere bei frühzeitigem Einsatz, die Sterblichkeit beim akuten Herzinfarkt wesentlich vermindern. Derzeit stehen vier unterschiedliche Thrombolytika (Streptokinase, APSAC, Urokinase und rt-PA) kommerziell zur Verfügung. Im klinischen Gebrauch unterscheiden sie sich insbesondere in der Geschwindigkeit, mit der sie die Thrombolyse herbeiführen, und in ihrer Fibrinspezifität. Inwieweit diese unterschiedlichen Eigenschaften die Prognose der Patienten wesentlich beeinflussen, wird derzeit noch kontrovers diskutiert.

Sofern Urokinase oder rt-PA zum Einsatz kommen, ist eine begleitende Heparintherapie unerläßlich. Um späteren Reinfarkten vorzubeugen, sollte - in Abhängigkeit vom klinischen Verlauf des Patienten - vor der Entlassung aus dem Krankenhaus oder im stabilen Intervall eine invasive Diagnostik mittels Herzkatheter und bei Vorhandensein höhergradiger Stenosen eine Dilatationsbehandlung oder Bypass-Operation durchgeführt werden.

Systemic recombinant tissue plasminogen activator lysis for left atrial thrombus formation after single-lung retransplantation

This report describes a recipient of single-lung transplantation surviving extraordinary complications: (1) early graft failure mandating retransplantation; (2) left atrial thrombus formation, which resolved by recombinant tissue plasminogen activator lysis; (3) and development of a "locked-in-syndrome." Possible underlying mechanisms are discussed.

Angioplasty of subacute and chronic total coronary occlusions: success, recurrence rate, and clinical follow-up

Angioplasty of single total, subacute, or chronic coronary occlusions was performed in 90 patients. It was successful in 54 occlusions (60%), in 77% of those less than 6 weeks old, and in 44% of those of greater than 6 weeks' duration (p less than 0.005). All procedures were uneventful. Control angiography was performed in 53 (98%) patients with successful angioplasty after an average interval of 97 +/- 53 days. Stenosis had recurred in 16 patients (30%). During a follow-up period of 36 +/- 13 months, three patients died, five patients underwent coronary bypass operation, and 10 had reangioplasty. Despite an additional late angiographic recurrence of stenosis in seven patients, 36 patients revealed angiographic long-term success. In the 46 nonoperated patients, angina pectoris and exercise stress tests were substantially improved. Thus angioplasty of subacute and chronic total coronary occlusions is an uneventful procedure, the success rate depending on the duration of the occlusions. Despite a high angiographic recurrence rate, the angiographic and clinical long-term results are favorable.

Increased thrombin levels during thrombolytic therapy in acute myocardial infarction. Relevance for the success of therapy

BACKGROUND

It has been suggested that thrombolysis in a feedback reaction may generate pro-coagulant activities.

METHODS AND RESULTS

Fifty-five patients were treated with urokinase-preactivated prourokinase (n = 35) or tissue-type plasminogen activator (n = 20) for acute myocardial infarction and underwent coronary angiography at 90 minutes and at 24-36 hours into thrombolysis, and fibrinogen (Ratnoff-Menzie), D-dimer (ELISA) and thrombin-antithrombin III complex levels (ELISA) were measured. Primary patency was achieved in 39 patients (70.9%), 13 of whom (33.3%) suffered early reocclusion. Nonsignificant decreases in fibrinogen levels were observed while D-dimer levels increased +3,008 +/- 4,047 micrograms/l (p less than 0.01), differences not being significant in respect to the thrombolytic agents or to the clinical course. In contrast, while thrombin-antithrombin III complex levels decreased -4.4 +/- 13.0 micrograms/l in patients with persistent patency, they increased +7.5 +/- 13.6 micrograms/l in case of nonsuccessful thrombolysis (p less than 0.02) and +11.9 +/- 23.8 micrograms/l in case of early reocclusion (p less than 0.001). For patients with thrombin-antithrombin III complex levels greater than 6 ng/l 120 minutes into thrombolysis, the unfavorable clinical course was predicted with 96.2% sensitivity and 93.1% specificity.

CONCLUSION

Generation of thrombin, occurring during thrombolysis, is a major determinant for the success of therapy and thrombin-antithrombin III levels may serve as predictors for the short-term prognosis.

[Percutaneous, transluminal angioplasty of aortocoronary venous bypass grafts--acute success, angiography and clinical follow-up]

In 41 consecutive patients with 49 stenoses of aorto-coronary venous bypass (ACVB) grafts percutaneous transluminal angioplasty (PTA) was attempted. PTA was successful, i.e., the percent area stenosis was reduced by greater than 20% to less than 70% (quantitative measurement with a precision magnifying lens from two orthogonal angiographic views) in 46 stenoses (94%) of 38 patients (93%). In 35 patients (92%) with 42 stenoses control coronary angiography was performed after a mean interval of 189 +/- 186 days. Recurrence, defined as an increase of percent area stenosis to greater than or equal to 70%, was found in nine stenoses (21%) of nine patients (26%). Recurrence correlated with a stenosis length greater than 10 mm before PTA (5/8 vs 4/32 stenoses: p less than 0.01). In recurrent stenoses, the average diameter of the grafted native coronary artery was significantly smaller than in recurrence-free stenoses (1.92 +/- 0.52 mm vs 2.45 +/- 0.50 mm; p less than 0.01). Clinical data were collected from all 38 patients with successful PTA after an average of 30 +/- 17 months following PTA. In this interval, 11 patients had undergone re-angioplasty and eight patients were re-operated; in addition, there were three cardiac deaths. In the 27 surviving patients without re-operation (71%), angina pectoris had improved from a mean of 3.0 +/- 0.7 before PTA to 1.8 +/- 1.0 (CCS-classification) (p less than 0.001). In 19 of the 27 patients (70%) the exercise stress test was negative, in contrast to only three patients (11%) before PTA. Thus, in the majority of patients PTA of ACVB-graft stenoses improves quality of life.(ABSTRACT TRUNCATED AT 250 WORDS)