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Biomedical subjects

S A Mousa

Publications and source records attributed to S A Mousa.

At least 91 records · Page 5Linked to original sources
PubMed1996

Expression of corticotropin-releasing factor in inflamed tissue is required for intrinsic peripheral opioid analgesia.

Immune cell-derived opioid peptides can activate opioid receptors on peripheral sensory nerves to inhibit inflammatory pain. The intrinsic mechanisms triggering this neuroimmune interaction are unknown. This study investigates the involvement of endogenous corticotropin-releasing factor (CRF) and interleukin-1beta (IL-1). A specific stress paradigm, cold water swim (CWS), produces potent opioid receptor-specific antinociception in inflamed paws of rats. This effect is dose-dependently attenuated by intraplantar but not by intravenous alpha-helical CRF. IL-1 receptor antagonist is ineffective. Similarly, local injection of antiserum against CRF, but not to IL-1, dose-dependently reverses this effect. Intravenous anti-CRF is only inhibitory at 10(4)-fold higher concentrations and intravenous CRF does not produce analgesia. Pretreatment of inflamed paws with an 18-mer 3'-3'-end inverted CRF-antisense oligodeoxynucleotide abolishes CWS-induced antinociception. The same treatment significantly reduces the amount of CRF extracted from inflamed paws and the number of CRF-immunostained cells without affecting gross inflammatory signs. A mismatch oligodeoxynucleotide alters neither the CWS effect nor CRF immunoreactivity. These findings identify locally expressed CRF as the predominant agent to trigger opioid release within inflamed tissue. Endogenous IL-1, circulating CRF or antiinflammatory effects, are not involved. Thus, an intact immune system plays an essential role in pain control, which is important for the understanding of pain in immunosuppressed patients with cancer or AIDS.

Analgesics, Opioid↗
PubMed1996

Oral antiplatelet, antithrombotic efficacy of DMP 728, a novel platelet GPIIb/IIIa antagonist.

BACKGROUND: Currently used antiplatelet drugs, including aspirin and ticlopidine, are effective against certain but not all of the many endogenous platelet activators. Because of their limited efficacy, a significant number of serious thromboembolic complications still occur, highlighting the need for a more effective therapy. DMP 728 has been characterized as a potent and specific platelet glycoprotein IIb/IIIa complex (GPIIb/IIIa) antagonist. The goals of the present study were to determine the oral antiplatelet and antithrombotic efficacies of DMP 728 in various arterial thrombosis models in dogs. METHODS AND RESULTS: In conscious and anesthetized mongrel dogs, DMP 728 at 0.02 to 1.0 mg/kg PO in gelatin capsules produced dose-dependent antiplatelet effects in inhibiting ex vivo platelet aggregation induced by ADP and prolonging template bleeding time. DMP 728 effects on bleeding time prolongation could be reversed more rapidly than those on platelet aggregation inhibition. A maximal antiplatelet effect for DMP 728 was demonstrated at 1.0 mg/kg PO. DMP 728 demonstrated dose-dependent oral antiplatelet effects with an absolute oral bioavailability of 8% to 12% in dogs. Additionally, the antithrombotic efficacy of DMP 728 was examined after intravenous and oral administration at different doses in various models of arterial thrombosis. In the coronary artery Folts' model in dogs, DMP 728 demonstrated maximal antithrombotic efficacy at 0.01 mg/kg IV and < 0.6 mg/kg PO. Additionally, DMP 728 at 0.1 and 1.0 mg/kg IV or PO demonstrated 60% to 100% prevention of primary thrombosis (P < .01) in an electrolytically induced carotid artery thrombosis model in dogs. CONCLUSIONS: These data suggest that DMP 728, a low-molecular-weight GPIIb/IIIa receptor antagonist, may have therapeutic potential as an oral antithrombotic agent in coronary and carotid artery thromboembolic disorders.

Adenosine Diphosphate↗
PubMed1996

Novel nonpeptide antiplatelet glycoprotein IIb/IIIa receptor antagonist, DMP754: receptor binding affinity and specificity.

OBJECTIVE: To define the antiplatelet efficacy and specificity of the glycoprotein IIb/IIIa complex (GPIIb/IIIa) antagonist prodrug DMP754 and its free acid form, XV459. METHODS AND MATERIALS: DMP754 has an IC50 > 1 mumol/l, and, upon its conversion with esterases to its free acid form, demonstrated high potency (IC50 20-45 nmol/l) in inhibiting human platelet aggregation induced by 10 mumol/l adenosine diphosphate, 20 micrograms/ml collagen, 1 mmol/l epinephrine, 10 mumol/l platelet activating factor or 0.5 IU/ml thrombin. The in-vitro rate of hydrolysis of DMP754 or XV459 is much faster with human or canine liver esterases (t 1/2 = 2.4-23 min) than with plasma esterases (t 1/2 = 5.5-7.6 h). Platelet GpIIb/IIIa integrin binding affinity and specificity for XV459 were determined using cell binding/adhesion assays. RESULTS: The range of IC50 values of XV459 in inhibiting platelet aggregation in platelet-rich plasma obtained from 12 subjects was 0.035-0.069 mumol/l with a mean IC50 of 0.050 +/- 0.003 mumol/l. Additionally, XV459 inhibited platelets obtained from mongrel dogs, baboons, sheep, guinea pigs, and mice with IC50 in the range 0.024-0.06 mumol/l, and IC50 in the range 0.16-5.8 mumol/l in pigs, rabbits, and rats. XV459 inhibited [125I]-fibrinogen binding to activated human platelets with an IC50 of 0.011 +/- 0.003 mumol/l. XV459 demonstrated a high degree of selectivity in specifically inhibiting fibrinogen binding to the platelet integrin, GPIIb/IIIa (IC50 = 0.00025 +/- 0.00005 mumol/l) compared with inhibiting other integrins (alpha v beta 3, IC50 > 10 mumol/l; or alpha v beta 5, alpha 5 beta 1, or alpha 4 beta 1, for which the IC50 exceeded 100 mumol/l). CONCLUSION: DMP754 is a potent antiplatelet agent in inhibiting platelet aggregation, and has a high specificity and affinity for human platelet GPIIb/IIIa receptors.

Amino Acids↗
PubMed1996

Antagonists of integrin alpha v beta 3 inhibit retinal neovascularization in a murine model.

Integrin alpha v beta 3 is differentially expressed in angiogenic blood vessels in skin granulation tissue, and alpha v beta 3 antagonists inhibit angiogenesis in chick chorioallantoic membranes. In this study, we investigated the role of alpha v beta 3 in retinal neovascularization. There was no detectable signal for alpha v beta 3 by immunohistochemistry in normal human retina, but neovascular tissue removed from the surface of the retina of patients with diabetic retinopathy showed intense staining for alpha v beta 3 within the endothelial cells of new blood vessels. In a murine model of oxygen-induced ischemic retinopathy, there was intense staining for alpha v beta 3 in endothelial cells participating in neovascularization but no detectable staining in normal retinal blood vessels of adult mice. Synthetic peptides that bind alpha v beta 3 and perturb alpha v beta 3-mediated adhesion in vitro inhibited retinal neovascularization in the murine model when given by intraperitoneal or periocular injections. These data suggest that alpha v beta 3 antagonists may provide a useful adjunct for the treatment of retinal neovascularization.

Animals↗
PubMed1995

Thrombospondin mediates calcium mobilization in fibroblasts via its Arg-Gly-Asp and carboxyl-terminal domains.

Thrombospondin is a matrix glycoprotein found in various cells that can modulate cell attachment, migration, and proliferation. We now show that intact soluble thrombospondin causes a transient [Ca2+]i increase in IMR-90 fibroblasts. This [Ca2+]i increase is mediated partly by the RGD-containing domain of thrombospondin that binds to the integrin alpha v beta 3 as demonstrated by inhibitor studies using anti-alpha v beta 3 antibody and RGD-containing peptides. A non-RGD and non-alpha v beta 3 component of this [Ca2+]i increase is mediated by the carboxyl-terminal domain of thrombospondin through an unidentified receptor on fibroblasts as shown by the antibody to the carboxyl-terminal of thrombospondin, C6.7. In addition, the carboxyl-terminal derived peptide, RFYVVMWK, also triggers [Ca2+]i increase in approximately 35% of fibroblasts. Both EGTA and Ni2+ block the entire [Ca2+]i increase indicating that this is due to an influx of extracellular Ca2+. B6H12, an antibody to the integrin-associated protein, blocks this [Ca2+]i increase by 50%, suggesting that some of the Ca2+ might be entering through an integrin-associated calcium channel. The current findings demonstrate that multiple domains on thrombospondin can trigger signal transduction events by increasing [Ca2+]i through their interactions with different cell receptors.

Amino Acid Sequence↗
PubMed1995

Platelet GPIIb/IIIa receptor occupancy studies using a novel fluoresceinated cyclic Arg-Gly-Asp peptide.

DMP 728 is a potent and specific platelet GPIIb/IIIa antagonist. Like all GPIIb/IIIa antagonists, DMP 728 has a steep dose-response relationship in inhibiting platelet aggregation. In this study the relationships between receptor occupancy, platelet aggregation and bleeding time was determined in anesthetized dogs after intravenous infusion of DMP 728 (0.01 and 0.1 mg/kg/2h). Receptor occupancy was determined by flow cytometry using XL086, a novel fluorescent cyclic RGD peptide that binds to GPIIb/IIIa with high specificity and affinity (kd approximately 55 nM). Mean number of GPIIb/IIIa as determined by flow cytometric assay was approximately 53,8000 and 79,000 on unactivated and ADP-activated platelets respectively. After DMP 728 intravenous infusion, there was a dose- and time-dependent increase in receptor occupancy, inhibition of platelet aggregation and bleeding time. The two methods of receptor occupancy determination correlate with each other with an r2 = 0.78. The present data suggest that blockade of only 40-60% (approximately 40,000 receptors) of the total platelet GPIIb/IIIa was required to achieve > 90% inhibition of platelet aggregation and > 15 min bleeding time. Our results showed the potential clinical utility of this approach in the study of GPIIb/IIIa dose-response relationship.

Amino Acid Sequence↗
PubMed1995

A monoclonal antibody that recognizes the GPIIb/IIIa antagonist DMP 728. Reversal of the effects of DMP 728 on platelet aggregation and bleeding time in the dog.

Since hemorrhagic events represent a major safety concern associated with the use of new antithrombotic therapies such as glycoprotein (GP) IIb/IIIa receptor blockade, we evaluated the ability of a monoclonal antibody recognizing DMP 728 (cyclic [D-2-aminobutyryl-N2-methyl-L-argininyl-glycyl-L-aspartyl-3- aminomethyl-benzoic acid] methanesulfonic acid salt), a potent GPIIb/IIIa receptor antagonist, to reverse the pharmacological actions of DMP 728 in the dog. DC11 was chosen for in vivo evaluation based on its ability to inhibit the binding of [3H]DMP 728 to activated platelets and to attenuate the inhibition of ADP-induced aggregation on platelet-rich plasma ex vivo by DMP 728. After anesthesia mongrel dogs were given DMP 728 (20 micrograms/kg body wt IV) infused into the femoral vein, bleeding times were determined using a Simplate device from incisions on the backside of the tongue, and platelet aggregation was determined ex vivo. Nearly complete inhibition of platelet aggregation was observed for the dogs treated with DMP 728 (20 ug/kg IV) for up to 210 minutes, and bleeding times were prolonged > 15 minutes for 2 hours and remained elevated for more than 4 hours. DC11 (0.2 or 1.0 mg/kg body wt IV) given to dogs 10 minutes after DMP 728 resulted in 50% attenuation of the effect of DMP 728 on aggregation at 3 hours. Approximately 34% inhibition of the DMP 728-mediated bleeding time was achieved at 1 hour with the 0.2 mg/kg dose, whereas approximately 50% inhibition of the bleeding time was observed for the 1 mg/kg dose at 1 hour.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Perineurial defect and peripheral opioid analgesia in inflammation.

Opioid receptors have been demonstrated on sensory nerves in both inflamed and normal subcutaneous tissue but locally applied opioid agonists produce analgesia in inflamed tissue only. Inflammation confers a disruption of the perineurial barrier that can also be induced deliberately by hyperosmolar solutions. The present study examines at which stage of Freund's adjuvant-induced inflammation peripheral opioid analgesic effects become manifest and whether a perineurial defect contributes to the appearance of such effects. To this end we have monitored the temporal evolution of inflammatory signs (swelling, temperature, hyperalgesia) and of peripheral antinociceptive effects (by the paw pressure test) of mu-, delta-, and kappa-selective opioids. Using horseradish peroxidase histochemistry, the perineurial barrier was assessed in normal and inflamed tissue and following its artificial disruption by hyperosmolar saline and mannitol in vivo. Finally, we sought to elicit analgesia in normal tissue by the concomitant application of mannitol and receptor-selective opioids or by an extremely lipophilic opioid agonist (fentanyl). We found that peripheral opioid antinociception and perineurial leakage occur simultaneously at a very early stage (within 12 hr) of the inflammatory reaction and that both can be mimicked by the administration of hyperosmolar solutions in normal tissue. Fentanyl produced peripheral antinociception in noninflamed tissue that was potentiated by mannitol or inflammation. Our findings demonstrate that the perineurium is a crucial determinant for peripheral opioid analgesia and that the efficacy of locally applied hydrophilic or lipophilic neuromodulatory compounds can be improved dramatically by the concomitant modulation of perineurial permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗
PubMed1994

Intravenous antiplatelet efficacy and safety of the platelet GPIIb/IIIa antagonist, DMP 728 in anesthetized dogs.

DMP 728, cyclo (D-2-aminobutyrate-N-Methyl-L-Arginyl-Glycyl-L-Aspartyl- 3-amino-methyl-benzoic acid) methanesulfonate salt, is a novel antiplatelet agent with high affinity and specificity for human and canine platelet GPIIb/IIIa (alpha 2/beta 3) receptors. DMP 728 demonstrated a potent antiplatelet efficacy in inhibiting ADP-induced platelet aggregation in either human or canine PRP with an IC50 of 0.046 and 0.015 microM, respectively. The IC50 of DMP 728 in inhibiting human platelet aggregation in PRP ranged from 0.02-0.05 microM regardless of the agonist used or even their combinations. Additionally, DMP 728 displayed a much greater affinity in inhibiting 125I-fibrinogen binding to stimulated human platelets as compared to the linear peptide RGDS or fibrinogen. The present study was undertaken to examine the i.v. antiplatelet efficacy and safety of DMP 728 in anesthetized dogs. In anesthetized mongrel dogs, DMP 728 (0.001-1.0 mg/kg, i.v. bolus) produced a dose-dependent inhibition of ex vivo platelet aggregation induced by ADP. The onset of inhibition was immediate, and the duration of antiplatelet effects was dose-dependent. A maximal inhibition of platelet aggregation and a reversible prolongation of bleeding time at 0.01 mg/kg were shown. Additionally, the antiplatelet efficacy/safety of DMP 728 was examined after i.v. administration at different infusion rates ranging from 0.008 to 0.833 micrograms/kg/min for 2 hours. A minimal antiplatelet effect was observed at the 0.008 micrograms/kg/min for 2 hours, while a maximal inhibition of platelet aggregation along with a reversible prolongation of bleeding time was achieved at 45-60 min post-infusion of 0.08 micrograms/kg/min x 2 hours. Prolongation of bleeding time was significantly reduced upon the cessation of the infusion while maximal inhibition of platelet aggregation was maintained longer. At all of the above regimens, DMP 728 did not result in any significant effects on platelet counts. Furthermore, DMP 728 did not elicit any other platelet unrelated adverse effects over wide range of doses. These data suggest that DMP 728, a low molecular weight platelet GPIIb/IIIa receptor antagonist, is a potent and systemically active antiplatelet agent with reversible effects on bleeding time.

Amino Acid Sequence↗
PubMed1994

Role of platelet GpIIb/IIIa receptors in the modulation of platelet plasminogen activator inhibitors type-1 (PAI-1) release.

This study was undertaken to determine the role of platelet glycoprotein (GP) IIb/IIIa receptors in the modulation of plasminogen activator type-1 (PAI-1) release from human platelets as compared to other platelet functions. To address this issue, the effect of various agonists on human platelet aggregation, [125I]fibrinogen binding and the release of PAI-1 was examined in normal and Glanzmann's thrombasthenic (GT) platelets. In control subjects, maximum platelet aggregation and PAI-1 secretion were observed within 5 min in response to the different agonists including thrombin, collagen, adenosine diphosphate (ADP), and arachidonic acid. Agonist-induced platelet GpIIb/IIIa receptor activation was confirmed by [125I]fibrinogen binding analysis. In contrast, platelets from GT subjects demonstrated a lack of fibrinogen binding and a lack of an aggregatory response to all agonists tested except to the GPIb- mediated aggregation induced by ristocetin. However, GT platelets demonstrated normal responsiveness in secreting PAI-1 in response to the various agonists. Similarly, when platelet GpIIb/IIIa receptors were blocked in normal platelets by the tripeptide Arg-Gly-Asp (RGD) or the tetrapeptide Arg-Gly-Asp-Ser (RGDS) at 10(-3) M, agonist-induced platelet aggregation and fibrinogen binding were blocked, but platelet PAI-1 release was not blocked. Furthermore, flow cytometric analysis using dual fluorescence markers for the platelet GPIIb/IIIa membrane receptors (FITC-labeled cyclic RGD analog, XL086) and for the alpha granule (PE-monoclonal antibody for P-selectin) demonstrated a dissociation between the platelet GPIIb/IIIa receptors and granular secretion. These results suggest a lack of a role for platelet GpIIb/IIIa receptors in the modulation of platelet PAI-1 release.

Amino Acid Sequence↗
PubMed1994

Antithrombotic effects of DMP 728, a platelet GPIIb/IIIa receptor antagonist, in a canine model of arterial thrombosis.

The platelet glycoprotein IIb/IIIa receptor (GPIIb/IIIa, fibrinogen receptor) represents the final common pathway for platelet aggregation. Inhibition of GPIIb/IIIa with antibodies or peptides containing the RGD sequence has been reported to prevent arterial thrombosis. We examined DMP 728 [(cyclic[D-2-amino-butyryl-N2-methyl-L-arginyl-glycyl-L-aspartyl-3-(a min o- methyl-benzoic acid], methanesulfonic acid salt], a cyclic peptidomimetic, GPIIb/IIIa receptor antagonist, for prevention of thrombosis and rethrombosis in a canine model of carotid artery thrombosis. Dogs were anesthetized, and both carotid arteries were instrumented with an electrode, a flow probe, and a stenosis. A 300-microA current was applied to the intimal surface in the right carotid artery (RCA, control) through the electrode; time to occlusive thrombus formation and thrombus mass was noted. The RCA served as the control vessel; the left carotid artery (LCA) served as the test vessel after DMP 728 administration (0.1 or 1. mg/kg, intravenously, i.v.). As compared with controls, occlusive thrombus formation was reduced by both doses of DMP 728 (control 100% n = 12; 0.1 mg/kg i.v. 17%, p < 0.05, n = 6; 1.0 mg/kg i.v. 0%, p < 0.05, n = 6), time to occlusion was increased (p < 0.05), and thrombus weight was reduced (p < 0.05). Ex vivo platelet aggregation was inhibited in all groups. In a second group of animals, a carotid artery thrombus was formed and lysed with anisoylated plasminogen activator complex (APSAC; 0.05 U/kg intraarterially, i.a.) with or without DMP 728.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Antiplatelet and antithrombotic efficacy of DMP 728, a novel platelet GPIIb/IIIa receptor antagonist.

BACKGROUND: Currently used antiplatelet drugs, including aspirin, ticlopidine, and others, are effective against certain but not all of the many endogenous platelet activators. Because of their limited efficacy, a significant number of serious thromboembolic complications still occur, highlighting the need for a more effective therapy. Thus, we have identified a systemically active peptide analogue (DMP 728) of the arginine-glycine-aspartic acid (RGD) recognition sequence that mediates the binding of ligands such as fibrinogen to the platelet glycoprotein (GP) IIb/IIIa receptors. The goals of the present study were to determine the antiplatelet and antithrombotic efficacies of DMP 728 in various arterial thrombosis models. METHODS AND RESULTS: DMP 728 demonstrated antiplatelet efficacy in vitro in inhibiting ADP-induced human platelet aggregation (IC50, 46 +/- 2 nmol/L) and fibrinogen binding to human platelets (IC50, 2.3 +/- 0.8 nmol/L) or purified human GPIIb/IIIa receptors (IC50, 0.6 +/- 0.1 nmol/L). DMP 728 demonstrated high affinity and specificity for human platelet GPIIb/IIIa over other adhesion molecules. In anesthetized mongrel dogs, DMP 728 at 0.001 to 1.0 mg/kg IV produced dose-dependent antiplatelet effects in inhibiting ex vivo platelet aggregation induced by ADP and in prolonging template bleeding time. DMP 728 effects on bleeding time prolongation were more rapidly reversible than those on platelet aggregation inhibition. A maximal antiplatelet effect for DMP 728 was demonstrated at 0.01 mg/kg IV bolus. The antithrombotic efficacy of DMP 728 was examined in vitro and in vivo after IV administration at different doses in various models of arterial thrombosis. In the coronary artery Folts model in dogs, DMP 728 demonstrated maximal antithrombotic efficacy at 0.01 mg/kg IV bolus with an ED50 of 0.005 mg/kg IV bolus in inhibiting cyclic flow reductions. Additionally, DMP 728 demonstrated 100% prevention of primary thrombosis and rethrombosis (P < .01) after treatment with different thrombolytics, including tissue plasminogen activator and streptokinase, in an electrolytically induced femoral artery thrombosis model in dogs. CONCLUSIONS: Acute intravenous DMP 728 administration (0.001 to 1.0 mg/kg) has dose-dependent antiplatelet and antithrombotic effects in different arterial thrombosis models. These data suggest that DMP 728, a low-molecular-weight GPIIb/IIIa receptor antagonist, may have therapeutic potential as an effective antithrombotic agent in coronary and peripheral artery thromboembolic disorders.

Angina, Unstable↗
PubMed1994

Thrombolytic and antithrombotic efficacy of the platelet GPIIb-IIIa antagonist DMP728.

OBJECTIVE: This study was undertaken to determine the antithrombotic and thrombolytic efficacy of DMP728 alone and in conjunction with thrombolytic agents. BACKGROUND: Coronary artery reocclusion continues to be a significant clinical problem after thrombolytic therapy or balloon angioplasty, with incidence rates of 5-20% regardless of thrombolytic intervention. To date, no adjunctive therapy has been shown to eliminate the incidence of rethrombosis after thrombolysis. DMP728, a novel small-molecular-weight platelet GPIIb-IIIa receptor antagonist, has been shown to prevent rethrombosis after thrombolysis in various arterial thrombosis models in dogs. It might therefore have potential utility in optimizing the clinical outcome of currently available thrombolytic agents. The present investigation was designed to examine the thrombolytic potential of DMP728 alone and in conjunction with different thrombolytic agents. METHODS: The deaggregatory effect of DMP728 in reversing human platelet aggregation after initiation of platelet aggregation by 10 mumol/l adenosine 5'-diphosphate was determined using light-transmittance aggregometry. The in-vitro efficacy of DMP728, alone and in combination with thrombolytic drugs, in dispersing a preformed platelet-rich clot was determined using a clot-dispersion assay. In addition, the in-vivo thrombolytic effects of DMP728, alone and in conjunction with streptokinase, were examined in an electrolytically induced femoral artery thrombosis model in dogs. RESULTS: DMP728 had concentration-dependent deaggregatory and thrombolytic effects in reversing aggregates and in dispersing a preformed platelet-rich thrombus in vitro. Furthermore, it exhibited significant potentiation (P < 0.01) when combined with different thrombolytic drugs such as streptokinase, tissue-type plasminogen activator (t-PA) and urokinase in lysing platelet-rich thrombus. DMP728 had significant in-vivo thrombolytic effects along with synergy in fully restoring arterial flow upon its concomitant use with subeffective to ineffective doses of streptokinase in an electrolytically induced femoral artery thrombosis model in dogs. It also reduced the time to reperfusion and prevented the incidence of rethrombosis after streptokinase. CONCLUSIONS: These findings suggest the potential utility and benefits of DMP728, not only in preventing arterial thrombosis but also in optimizing the efficacy of thrombolytic drugs.

Adenosine Diphosphate↗
PubMed1994

Recombinant plasminogen activator inhibitor type 1: a review of structural, functional, and biological aspects.

Plasminogen activator inhibitor type 1 (PAI-1), a member of the serpin family of serine protease inhibitors, inhibits both tissue-type plasminogen activator (t-PA) and urokinase type plasminogen activator (u-PA). High PAI-1 levels are associated with an increased risk of thromboembolic disease while PAI-1 deficiency may represent an inherited autosomal recessive bleeding disorder. This review describes the biochemistry of PAI-1 including its purification, conversion between active and latent forms, and interaction with its target serine proteases and its protein cofactor, vitronectin. In addition, an overview of animal studies with PAI-1 is presented to examine its role in regulating fibrinolysis in vivo. For this review, particular emphasis is placed on studies with a recombinant form of bacterially expressed PAI-1 (rPAI-1), which shares many features in common with the active form of native PAI-1.

Animals↗
PubMed1993

Recombinant plasminogen activator inhibitor-1 protects platelets against the inhibitory effects of plasmin.

Plasmin-induced degradation of platelet glycoprotein Ib (GPIb), the von Willebrand factor (vWF) receptor, has been implicated as a mechanism contributing to the development of platelet dysfunction following cardiopulmonary bypass (CPB). The goal of this study was to assess whether biologically active recombinant plasminogen activator inhibitor-1 (rPAI-1), could antagonize the inhibitory effects of plasmin on GPIb. GPIb function, as evaluated by measuring vWF-dependent, ristocetin-induced platelet agglutination in human platelet rich plasma (PRP) was significantly impaired following incubation with plasmin (60 +/- 14% inhibition, p < 0.01). Inclusion of rPAI-1 (10 micrograms/ml) in the PRP antagonized this plasmin effect, restoring agglutination to 92 +/- 8% of the control value (p < 0.01). The effect of rPAI-1 on the enzymatic activity of plasmin was further evaluated in an amidolytic assay with the plasmin substrate S2251 where an apparent second order rate constant of plasmin inhibition by rPAI-1 of 9.4 x 10(4) M-1 S-1 was determined. Our results suggest that rPAI-1, by inhibiting both tissue plasminogen activator-induced plasmin generation and plasmin activity directly, may have clinical value for improving platelet function during and after CPB.

Fibrinolysin↗