-
Journal of the American College of... Nov 1987Recombinant tissue-type plasminogen activator (rt-PA) and single chain urokinase-type plasminogen activator (scu-PA) are thrombolytic agents, characterized by a high but... (Review)
Review
Recombinant tissue-type plasminogen activator (rt-PA) and single chain urokinase-type plasminogen activator (scu-PA) are thrombolytic agents, characterized by a high but not absolute degree of fibrin specificity that is mediated through different molecular mechanisms. Both activators are still under clinical investigation but it has become apparent that their therapeutic dose in humans is high and associated with a variable degree of systemic activation of the fibrinolytic system and fibrinogen breakdown. Therefore, the quest for further improvement of agents and therapeutic schemes continues. Research is being pursued in this area along the following lines: 1) tissue-type plasminogen activator (t-PA) and single chain urokinase-type plasminogen activator in molar ratios of 4:1 to 1:4 do not act synergistically on thrombolysis in a plasma environment in vitro, but display significant synergism in animal models of thrombosis. In pilot studies in patients with coronary artery occlusion, rt-PA and scu-PA are markedly synergistic and efficient thrombolysis can be obtained with a fivefold lower combined dose than that of the separate agents. The combined dose does not seem to induce systemic fibrinogen breakdown. 2) Deletion mutants of rt-PA can be constructed with a significantly prolonged half-life in vivo, and a better thrombolytic potential after bolus intravenous injection. 3) Cleavage site-specific mutants of scu-PA that abolish the conversion to urokinase may have a higher fibrin specificity. The mutants constructed thus far, however, seem to have a lower specific thrombolytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Drug Synergism; Fibrinolysis; Fibrinolytic Agents; Humans; Mutation; Plasminogen Activators; Recombinant Proteins; Structure-Activity Relationship; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator
PubMed: 3117858
DOI: 10.1016/s0735-1097(87)80422-9 -
The Israel Medical Association Journal... Nov 2006Acute ischemic stroke is one of the leading causes of mortality and chronic disability in the western world. Yet, despite the enormous socioeconomic burden that it... (Review)
Review
Acute ischemic stroke is one of the leading causes of mortality and chronic disability in the western world. Yet, despite the enormous socioeconomic burden that it imposes, therapies to combat AIS are not widely available. Moreover, revascularization of the ischemic tissue with tissue plasminogen activator, the only FDA-approved therapy for AIS, is hampered by a very narrow therapeutic time window and is only used in a minority of patients. Cerebral ischemia leads to brain damage caused by several pathologic mechanisms that can potentially be blocked by neuroprotective drugs that aim to salvage the ischemic penumbra. However, despite numerous clinical trials, no single drug candidate has proved efficacious in AIS. The current situation calls for novel therapeutic strategies to be used in acute ischemic stroke. This review surveys some of these novel and promising cutting edge therapies.
Topics: Benzenesulfonates; Humans; Membrane Proteins; Myocardial Revascularization; Neuroprotective Agents; Plasminogen Activators; Randomized Controlled Trials as Topic; Stroke; Tetraspanins; Tissue Plasminogen Activator
PubMed: 17180832
DOI: No ID Found -
Schweizerische Medizinische... Nov 1987Human plasma contains two physiologic activators of the fibrinolytic system: prourokinase, also called single chain urokinase-type plasminogen activator (scu-PA), and... (Comparative Study)
Comparative Study Review
Human plasma contains two physiologic activators of the fibrinolytic system: prourokinase, also called single chain urokinase-type plasminogen activator (scu-PA), and tissue-type plasminogen activator (t-PA). Both activators can catalyze the proenzyme plasminogen to plasmin. Plasmin transforms fibrin into soluble fibrin breakdown products. t-PA is an inefficient plasminogen activator in the absence of fibrin. In the presence of fibrin, t-PA and plasminogen bind to fibrin; the resultant ternary complex increases the efficiency of the transformation of plasminogen to plasmin two to five hundred times. The activity of the fibrinolytic system is modulated by inhibitors. alpha 2-antiplasmin forms 1:1 stochiometric complexes with plasmin and thus neutralizes circulating plasmin with exceptional rapidity. A specific plasminogen activator-inhibitor has recently been described which rapidly inactivates t-PA and urokinase. The fibrin-specific thrombolytic t-PA has undergone intensive clinical trials, particularly in acute myocardial infarction. It has been found that t-PA is better tolerated (bleeding) while being at least as effective, or more so, than streptokinase. Several research groups are attempting through gene manipulation to produce t-PA with even better therapeutic effect (e.g. even better binding to fibrin, longer half life). Clinical trials of prourokinase and combined prourokinase/t-PA are under way and have also provided favourable therapeutic results so far.
Topics: Drug Therapy, Combination; Fibrinolysis; Fibrinolytic Agents; Humans; Myocardial Infarction; Plasminogen Activators; Streptokinase; Thromboembolism; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator
PubMed: 3122317
DOI: No ID Found -
The New England Journal of Medicine Mar 1984Tissue-type plasminogen activator is a naturally occurring, clot-selective activator of fibrinolysis. We recently reported that human tissue-type plasminogen activator... (Comparative Study)
Comparative Study
Tissue-type plasminogen activator is a naturally occurring, clot-selective activator of fibrinolysis. We recently reported that human tissue-type plasminogen activator isolated from a Bowes-melanoma-tissue-culture supernate lysed coronary thrombi in dogs without depleting circulating fibrinogen or alpha 2-antiplasmin, in contrast to the case with streptokinase and urokinase. In the present study coronary thrombolysis, confirmed angiographically, was induced within 19 to 50 minutes with intravenous or intracoronary tissue-type plasminogen activator in six of seven patients with evolving myocardial infarction. Circulating fibrinogen, plasminogen, and alpha 2-antiplasmin were not depleted by this agent, in contrast to the case in the two patients subsequently given streptokinase. In the one patient in whom lysis was not inducible with tissue-type plasminogen activator, it was also not inducible with streptokinase. These observations indicate that clot-selective coronary thrombolysis can be induced in patients with evolving myocardial infarction by means of tissue-type plasminogen activator, without concomitant induction of a systemic lytic state. Definition of its therapeutic benefit must await greater availability of the agent and the performance of appropriate clinical trials.
Topics: Aged; Coronary Vessels; Drug Evaluation; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Humans; Middle Aged; Myocardial Infarction; Plasminogen; Plasminogen Activators; Streptokinase; alpha-2-Antiplasmin
PubMed: 6537987
DOI: 10.1056/NEJM198403083101001 -
The Journal of Investigative Dermatology Jun 1988To investigate the role of plasminogen activator (PA) in cutaneous disease, we have used biochemical and immunocytochemical techniques to examine PA in normal and...
To investigate the role of plasminogen activator (PA) in cutaneous disease, we have used biochemical and immunocytochemical techniques to examine PA in normal and lesional skin. In normal human dermis, tissue PA is the predominant PA activity; however, in normal epidermis, urokinase type PA is the predominant PA activity. In contrast, PA activity in epidermis from lesions of patients with a variety of cutaneous diseases was predominantly tissue type enzyme with a much smaller contribution from urokinase. Our patient population included individuals with benign chronic pemphigus, pemphigus vulgaris, pemphigus foliaceous, bullous pemphigoid, or psoriasis. Using rabbit antibody specific for tissue type PA, we have immunocytochemically localized this enzyme in lesions from individuals with the above disorders. Our results indicate that tissue PA is consistently elevated in cutaneous lesions with diverse etiology, pathology, and clinical presentation.
Topics: Adult; Epidermis; Humans; Plasminogen Activators; Skin Diseases; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator
PubMed: 3131439
DOI: 10.1111/1523-1747.ep12461494 -
Experimental Eye Research Mar 1989Anterior keratectomy was performed to 10 eyes of 8 adult rabbits. The animals were killed 3-24 hr after wound closure. The corneas were excised and subjected to...
Anterior keratectomy was performed to 10 eyes of 8 adult rabbits. The animals were killed 3-24 hr after wound closure. The corneas were excised and subjected to histochemical demonstration of urokinase-type plasminogen activator (u-PA), tissue-type PA (t-PA) and plasminogen activator inhibitor [PAI-1) using commercial antibodies. A strong immunoreaction for u-PA, a weaker reaction for PAI-1 and a very weak t-PA-like immunoreaction appeared in the anterior stroma of the wounded area. None of the antisera used showed any immunostaining in the cornea outside the wound. The role of the plasminogen activator-plasmin system in the healing of the corneal wound is discussed.
Topics: Animals; Cornea; Corneal Injuries; Glycoproteins; Plasminogen Activators; Plasminogen Inactivators; Rabbits; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator; Wound Healing
PubMed: 2494049
DOI: 10.1016/s0014-4835(89)80012-0 -
Biochimica Et Biophysica Acta Sep 1979A procedure was developed for the purification of a plasminogen activator from human uterine tissue. It involves six consecutive steps: (1) extraction of the plasminogen...
A procedure was developed for the purification of a plasminogen activator from human uterine tissue. It involves six consecutive steps: (1) extraction of the plasminogen activator from delipidated uterine tissue with 0.3 M potassium acetate buffer, pH 4.2; (2) ammonium sulphate precipitation; (3) zinc chelate-agarose chromatography; (4) n-butyl-agarose chromatography; (5) concanavalin A-agarose chromatography; and (6) gel filtration on Sephadex G-150. The specific activity of the final plasminogen activator preparation was increased by a factor 4500 as compared with the crude extract. The purified plasminogen activator showed a strong tendency to adsorb to surfaces. This could be effectively prevented by Tween-80. The molecular weight of the plasminogen activator was 64 000 as estimated by gel filtration in 1.0 M NaCl and 69 000 as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The plasminogen activator consisted of two chains (molecular weights 31 000 and 38 000) connected by disulphide bridges. The smallest chain contained the serine residue of the active site as deduced from the incorporation of the tritium label of [3H]diisopropylphosphofluoridate.
Topics: Binding Sites; Chemical Phenomena; Chemistry; Chromatography; Female; Humans; Isoflurophate; Molecular Weight; Plasminogen Activators; Plasminogen Inactivators; Uterus
PubMed: 121055
DOI: 10.1016/0005-2795(79)90205-8 -
Analytical Biochemistry Feb 1988An electrophoretic modification of the conventional fibrin autography that can be used for the detection of plasminogen activators (urokinase type and tissue type) and...
An electrophoretic modification of the conventional fibrin autography that can be used for the detection of plasminogen activators (urokinase type and tissue type) and fibrin-degrading enzymes in complex biological fluids is described. After separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the proteins and the substrate plasminogen are transferred electrophoretically into the fibrin indicator gel, resulting in an efficient transfer of proteinases as well as high resolution and contrast of fibrinolytic zones caused by plasminogen activator activity. Picogram amounts of human urokinase type plasminogen activator (about 0.002 International Unit) are still detectable. The technique is also applicable to reversed fibrin autography for plasminogen activator inhibitors.
Topics: Electrophoresis, Polyacrylamide Gel; Fibrin; Plasminogen; Plasminogen Activators
PubMed: 3364738
DOI: 10.1016/0003-2697(88)90337-5 -
Thrombosis Research Jul 1989The plasminogen activator activity (PAA) in extracts of the intima, media, and adventitia of the normal human aorta and other large arteries (carotid artery, renal...
Demonstration of plasminogen activator activity in the intima and media of the normal human aorta and other large arteries: immunological identification of the plasminogen activator(s).
The plasminogen activator activity (PAA) in extracts of the intima, media, and adventitia of the normal human aorta and other large arteries (carotid artery, renal artery and iliac artery) was studied with a sensitive, quantitative spectrophotometric assay using plasminogen and the chromogenic plasmin substrate S-2251. All layers of the arteries showed PAA which was highest in the adventitia, lowest in the media, while in the intima (aorta) PAA was intermediate, but much closer to that of the media. Plasminogen activator inhibition (PAI) was at the same level in all layers of the arteries studied. Plasmin inhibition (PI) was higher in adventitia than in intima (aorta), while in media the PI was intermediate. The PAA was due to the tissue-type plasminogen activator (t-PA), but not to the urokinase-type (u-PA), as judged by addition of respective antibodies. The relatively low PAA found in the intima of large arteries is therefore due to a low plasminogen activator and not a high plasminogen activator inhibitor activity or plasmin inhibitor level.
Topics: Adolescent; Antibodies; Aorta; Arteries; Child; Fibrinolysin; Humans; Plasminogen Activators; Plasminogen Inactivators; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator
PubMed: 2528844
DOI: 10.1016/0049-3848(89)90443-x -
Journal of the American College of... Nov 1987Since streptokinase and urokinase became available for clinical use, numerous attempts have been made to improve these useful thrombolytic agents. To decrease its... (Review)
Review
Since streptokinase and urokinase became available for clinical use, numerous attempts have been made to improve these useful thrombolytic agents. To decrease its antigenicity, streptokinase has been fragmented or coupled to human plasminogen or polyethylene glycols. With a plasmin B chain-streptokinase complex a more potent agent was obtained. To prolong their half-life, streptokinase and urokinase were immobilized with water-soluble carriers. Coupling urokinase with fibrin-specific antibodies increases its thrombolytic efficacy, at least in vitro. The only thrombolytic agents with a relative fibrin specificity available for clinical purposes are tissue-type plasminogen activator and single chain urokinase-type plasminogen activator. Mutants and hybrids of these molecules are being constructed and may further improve their fibrin specificity and therapeutic potential.
Topics: Drug Combinations; Enzymes, Immobilized; Fibrinolysin; Fibrinolysis; Fibrinolytic Agents; Humans; Mutation; Plasminogen; Plasminogen Activators; Polyethylene Glycols; Recombinant Proteins; Streptokinase; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator
PubMed: 2959714
DOI: 10.1016/s0735-1097(87)80421-7