Reduction of early vein graft thrombosis by tissue plasminogen activator gene transfer

2009 ◽  
Vol 102 (07) ◽  
pp. 145-152 ◽  
Author(s):  
Marcella J. Wyatt ◽  
Andrew C. Newby ◽  
Anita C. Thomas
Keyword(s):  
Blood Flow ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Ex Vivo ◽  
Arterial Stenosis ◽  
Graft Thrombosis ◽  
Vein Grafts ◽  
Cyclic Flow ◽  
Tissue Plasminogen ◽  
Early Graft

SummaryVein grafts are used to bypass coronary arterial stenosis, but many grafts thrombose soon after surgery. A model was developed in the pig to allow continuous measurement of blood flow and production of flow-restricting thrombi (cyclic flow reductions; CFRs). Saphenous vein lumen was exposed to adenovirus ex vivo, to over-express human tissue plasminogen activator (h-tPA), with β-galactosidase adenovirus as a control. The vein segmen ts were engrafted into carotid arteries and examined 0,1 or 3 days later (4–7 animals/group). Untransduced grafts examined on the day of surgery developed repeated CFRs at both normal and restricted flow, but their frequency declined in grafts examined after 3 days. Adenovirus transduction was evident as β-galactosidase or h-tPA expression 1 day after engraftment. Blood flow was increased 1.4-fold in h-tPA transduced grafts after 1 day [control 390 (280–510), h-tPA 550 (450–660) ml/min; p=0.02 (expressed as mean (95% confidence intervals)]. CFRs were less severe (p=0.002) in the h-tPA transduced grafts than β-galactosidase-transduced grafts. CFRs were also less frequent in unstenosed undamaged h-tPA grafts [control 17 (6.1–29), h-tPA 7.6 (1.7–14) CFR/hr; p=0.02], but this difference was reduced after damage or stenosis. CFRs formed faster in h-tPA than in β-galactosidase-transduced grafts [control 14 (11–17), h-tPA 23 (19–27) ml/min2; p<0.001], and resolved twofold faster [control 25 (22–30), h-tPA 48 (39–60) ml/min2; p<0.001]. Hence, in this model, local gene therapy with h-tPA increased graft blood flow and decreased measures of early graft thrombosis, namely quicker CFR resolution and decreased frequency and severity.

scholarly journals Effect of Delayed Thrombolysis with rt-PA in a Rat Embolic Stroke Model

1994 ◽  
Vol 14 (3) ◽  
pp. 472-477 ◽  
Author(s):  
Karsten Overgaard ◽  
Tomas Sereghy ◽  
Hans Pedersen ◽  
Gudrun Boysen
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Thrombolytic Therapy ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Infarct Volume ◽  
Embolic Stroke ◽  
Stroke Model ◽  
Tissue Plasminogen ◽  
Before And After

The effect of delayed thrombolysis with recombinant tissue plasminogen activator was tested in an embolic stroke model. The carotid territory was embolized in 103 rats with fibrin-rich clots formed and washed in polyethylene tubes. Hemispheric cerebral blood flow before and after embolization was measured by the intra arterial 133Xe injection method. At five delay times, 15–240 min after embolization, 69 animals were treated with tissue plasminogen activator, 20 mg/kg, and 34 animals with saline. Carotid angiography displayed the grade of occlusion of the cerebral arterial supply before and after treatment. Brains were fixed after 2 days, evaluated neuropathologically, and infarct volume measured. Cerebral blood flow was reduced by 56–71% after embolization. Reperfusion induced by thrombolytic therapy was demonstrated by comparing the posttreatment angiography of the pooled five treatment groups to control animals. Thrombolytic therapy significantly reduced the infarct volume and improved the prekill clinical score by up to 2 h of treatment delay, and treatment might have been beneficial even after 4 h delay. Prolonging the delay of treatment increased the infarct volume ( p < 0.001, Jonckheere–Terpstra test). Only a few hemorrhagic complications were observed. Thus, thrombolytic therapy in embolic stroke induced recanalization. The effect on clinical outcome and infarct volume was dependent on delay time.

scholarly journals A kinetic model of the circulatory regulation of tissue plasminogen activator during exercise, epinephrine infusion, and endurance training

Blood ◽  
1993 ◽  
Vol 81 (12) ◽  
pp. 3293-3302
Author(s):  
WL Chandler ◽  
WC Levy ◽  
RC Veith ◽  
JR Stratton
Keyword(s):  
Blood Flow ◽  
Endurance Training ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Hepatic Blood Flow ◽  
Plasma Epinephrine ◽  
Epinephrine Infusion ◽  
Tissue Plasminogen ◽  
Pai 1 ◽  
Epinephrine Concentration

A computer simulation of the circulatory system was used to kinetically model secretion, inhibition, and clearance of tissue plasminogen activator (t-PA) during three different processes that increase active t-PA levels: epinephrine infusion, exercise, and endurance training. Infusion of epinephrine stimulated an increase in t-PA secretion that was proportional to the plasma epinephrine concentration. In addition, epinephrine infusion increased hepatic blood flow and t-PA clearance, thus slowing the increase of plasma t-PA levels. During exercise, t-PA levels increased due both to increased t-PA secretion and to decreased clearance secondary to reduced hepatic blood flow. The increase in t-PA secretion during exercise was directly proportional to the epinephrine concentration in blood with the same ratio of t-PA secretion to epinephrine as found during epinephrine infusion, suggesting that increased plasma epinephrine during exercise was the primary stimulus for t-PA secretion. Lastly, the simulation predicted that 6 months of endurance training produced a decrease in resting plasminogen activator inhibitor type 1 (PAI-1) secretion, resulting in less t-PA inhibition and an overall increase in active t-PA after training. Accurate analysis of the regulation of active t-PA levels in blood required simultaneous modeling of t-PA and PAI-1 secretion, hepatic clearance, and inhibition of t-PA by PAI-1.

The Effect of Thrombin Inhibitors on Tissue Plasminogen Activator Induced Thrombolysis in a Rat Model

1992 ◽  
Vol 68 (01) ◽  
pp. 064-068 ◽  
Author(s):  
Petr Klement ◽  
Anita Borm ◽  
Jack Hirsh ◽  
John Maraganore ◽  
Gregory Wilson ◽  
...  
Keyword(s):  
Blood Flow ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Rat Model ◽  
Antithrombin Iii ◽  
Balloon Catheter ◽  
Thrombin Inhibitors ◽  
Thrombin Inhibitor ◽  
Limited Effectiveness ◽  
Tissue Plasminogen

SummarySuccessful coronary thrombolysis depends on rapidly restoring blood flow and maintaining patency of the infarct-related artery. Although widely used as an adjunct to lytic therapy, heparin is limited in its ability to produce these effects. Since the limitations of heparin may reflect its inability to inactivate clot-bound thrombin, we developed a rat model of tissue plasminogen activator (t-PA) induced thrombolysis to compare doses of heparin, hirudin, hirulog (a synthetic hirudin-derived peptide), and D-Phe-Pro-ArgCH2Cl (PPACK) that produced a 4-fold prolongation of the baseline activated partial thromboplastin time (APTT) with saline in terms of their ability to accelerate thrombolysis and to prevent reocclusion. A thrombus rich in red cells and fibrin was formed in the distal aorta by applying an external constrictor after denuding the endothelium with a balloon catheter. Thrombolysis was induced with t-PA (1 mg/kg bolus, followed by 1 mg kg–1 h–1 over 30 min) and the rats were then randomized to receive a concomitant 80 min infusion of a thrombin inhibitor or saline. By continuously monitoring blood flow and pre- and post-stenotic blood pressures, the time to clot lysis, and the number of reocclusions were determined. Compared to saline, heparin had no significant effect on these variables. In contrast, hirudin, hirulog, and PPACK significantly (p <0.01) increased the percentage of the time that the vessel remained patent from 63.9 ± 7.7 to 90.7 ± 2.2, 94.0 ± 0.9, and 94.7 ± 1.0%, respectively by significantly (p <0.01) decreasing the number of reocclusions. The superiority of the antithrombin III-independent inhibitors over heparin supports the hypothesis that the limited effectiveness of heparin in this setting reflects its inability to inactivate clot-bound thrombin. Compared to saline, hirulog and PPACK also significantly (p <0.02) accelerated the time to thrombolysis from 10.5 ± 2.3 to 4.4 ± 0.6, and 4.2 ± 0.8 min, respectively, whereas heparin and hirudin did not. The ability of the lower molecular weight inhibitors of thrombin to accelerate lysis may reflect their greater accessibility to clot-bound thrombin. These findings raise the possibility that the antithrombin III-independent inhibitors of thrombin may not be equally effective as adjuncts to thrombolytic therapy with t-PA.

scholarly journals A kinetic model of the circulatory regulation of tissue plasminogen activator during exercise, epinephrine infusion, and endurance training

Blood ◽  
1993 ◽  
Vol 81 (12) ◽  
pp. 3293-3302 ◽  
Author(s):  
WL Chandler ◽  
WC Levy ◽  
RC Veith ◽  
JR Stratton
Keyword(s):  
Blood Flow ◽  
Endurance Training ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Hepatic Blood Flow ◽  
Plasma Epinephrine ◽  
Epinephrine Infusion ◽  
Tissue Plasminogen ◽  
Pai 1 ◽  
Epinephrine Concentration

Abstract A computer simulation of the circulatory system was used to kinetically model secretion, inhibition, and clearance of tissue plasminogen activator (t-PA) during three different processes that increase active t-PA levels: epinephrine infusion, exercise, and endurance training. Infusion of epinephrine stimulated an increase in t-PA secretion that was proportional to the plasma epinephrine concentration. In addition, epinephrine infusion increased hepatic blood flow and t-PA clearance, thus slowing the increase of plasma t-PA levels. During exercise, t-PA levels increased due both to increased t-PA secretion and to decreased clearance secondary to reduced hepatic blood flow. The increase in t-PA secretion during exercise was directly proportional to the epinephrine concentration in blood with the same ratio of t-PA secretion to epinephrine as found during epinephrine infusion, suggesting that increased plasma epinephrine during exercise was the primary stimulus for t-PA secretion. Lastly, the simulation predicted that 6 months of endurance training produced a decrease in resting plasminogen activator inhibitor type 1 (PAI-1) secretion, resulting in less t-PA inhibition and an overall increase in active t-PA after training. Accurate analysis of the regulation of active t-PA levels in blood required simultaneous modeling of t-PA and PAI-1 secretion, hepatic clearance, and inhibition of t-PA by PAI-1.

scholarly journals DNA Vaccine Combinations Expressing Either Tissue Plasminogen Activator Signal Sequence Fusion Proteins or Ubiquitin-Conjugated Antigens Induce Sustained Protective Immunity in a Mouse Model of Pulmonary Tuberculosis

2002 ◽  
Vol 70 (1) ◽  
pp. 292-302 ◽  
Author(s):  
Giovanni Delogu ◽  
Amy Li ◽  
Charlene Repique ◽  
Frank Collins ◽  
Sheldon L. Morris
Keyword(s):  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Dna Vaccine ◽  
Ex Vivo ◽  
Signal Sequence ◽  
Lung Pathology ◽  
Intracellular Targeting ◽  
Tissue Plasminogen ◽  
Efficacious Vaccine ◽  
Cellular Immune

ABSTRACT DNA vaccination has emerged as a powerful approach in the search for a more efficacious vaccine against tuberculosis. In this study, we evaluated the effectiveness of immunizing with combinations of 10 different tuberculosis DNA vaccines that expressed mycobacterial proteins fused at the N terminus to eukaryotic intracellular targeting sequences. In one vaccine combination, the genes were fused to the tissue plasminogen activator signal sequence (TPA), while in a second combination the same 10 genes were expressed as ubiquitin (Ub)-conjugated proteins. In ex vivo studies in which the secretion of gamma interferon was measured, cellular immune responses were detected in mice vaccinated with either the TPA DNA vaccine combination or the Ub DNA vaccine combination at 7 and 14 days following a low-dose Mycobacterium tuberculosis challenge. Moreover, mice vaccinated with the TPA combination, the Ub combination, and Mycobacterium bovis BCG were able to limit the growth of tubercle bacilli in the lung and spleen after a virulent tuberculous aerosol challenge. Histopathological analyses also showed that mice immunized with the DNA vaccine combinations had substantially improved postinfection lung pathology relative to the naïve controls. Finally, in three different long-term experiments, the survival periods following aerogenic challenge were extended as much as sevenfold for vaccinated mice compared to naïve controls. Interestingly, in all three experiments, no significant differences were detected in the mean times to death for mice immunized with the TPA combination or the Ub combination relative to the BCG controls. In conclusion, these studies demonstrate the effectiveness of immunization with DNA vaccine combinations against tuberculosis and suggest that further testing of these plasmid cocktails is warranted.

scholarly journals PGE1 accelerates thrombolysis by tissue plasminogen activator

Blood ◽  
1989 ◽  
Vol 73 (5) ◽  
pp. 1213-1217
Author(s):  
DE Vaughan ◽  
SR Plavin ◽  
AI Schafer ◽  
J Loscalzo
Keyword(s):  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Prostaglandin E1 ◽  
Active Element ◽  
Ex Vivo ◽  
Plasminogen Activators ◽  
Platelet Inhibition ◽  
Clot Lysis ◽  
Half Time ◽  
Tissue Plasminogen

Platelets are an active element in the generation of thrombus and may influence rates of thrombolysis during the administration of plasminogen activators. To assess the potential importance of platelet aggregation in the thrombolytic response to plasminogen activators, we measured rates of thrombolysis induced by tissue plasminogen activator in the presence and absence of a coinfusion of prostaglandin E1 in a rabbit jugular vein model of thrombosis. Rates of lysis were quantified by measuring the half-time for lysis of the thrombus. At all concentrations of tissue plasminogen activator used, prostaglandin E1 markedly reduced the half-time for clot lysis and enhanced somewhat the overall extent of thrombolysis, without affecting significantly either the degree of fibrinogen depletion or the animals' mean arterial pressures. These effects on thrombolytic efficacy were accompanied by ex vivo evidence of platelet inhibition. These data suggest that the antiplatelet prostaglandin E1 may be a very useful adjunctive agent in thrombolytic therapy primarily by virtue of the significant improvement in the rate of thrombolysis that its use affords.

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