Anti-thrombotic Effect of a PAI-1 Inhibitor in Rats Given Endotoxin

1996 ◽  
Vol 75 (01) ◽  
pp. 118-126 ◽  
Author(s):  
T Abrahamsson ◽  
V Nerme ◽  
M Strömqvist ◽  
B Åkerblom ◽  
A Legnehed ◽  
...  
Keyword(s):  
Plasminogen Activator Inhibitor ◽  
Rat Plasma ◽  
Clot Lysis ◽  
Fibrin Deposition ◽  
Plasminogen Activator Inhibitor 1 ◽  
Fab Fragment ◽  
Dose Dependent Decrease ◽  
Pai 1

SummaryThe aim of this study was to investigate the anti-thrombotic effects of an inhibitor of the plasminogen activator inhibitor-1 (PAI-1) in rats given endotoxin. In studies in vitro, PRAP-1, a Fab-fragment of a polyclonal antibody against human PAI-1, was shown to inhibit PAI-1 activity in rat plasma as well as to stimulate clot-lysis of the euglobulin fraction derived from rat plasma. Endotoxin administered to anaesthetised rats produced a marked increase in plasma PAI-1 activity. To study fibrin formation and lysis in vivo after intravenous (i. v.) injection of the coagulant enzyme batroxobin, 125I-fibrinogen was administered to the animals. The thrombi formed by batroxobin were rapidly lysed in control animals, while the rate of lysis was markedly attenuated in rats given endotoxin. PRAP-1 was administered i.v. (bolus + infusion) to rats given endotoxin and batroxobin and the PAI-1 inhibitor caused a dose-dependent decrease in the 125I-fibrin deposition in the lungs. An immunohistochemical technique was used to confirm this decrease in density of fibrin clots in the tissue. Furthermore, PRAP-1 decreased plasma PAI-1 activity in the rats and this reduction was correlated to the decrease in lung 125I-fibrin deposition at the corresponding time point. It is concluded that in this experimental model the PAI-1 antibody PRAP-1 may indeed inhibit thrombosis in animals exposed to endotoxin.

The Roles of α2-Antiplasmin and Plasminogen Activator Inhibitor 1 (PAI-1) in the Inhibition of Clot Lysis

1993 ◽  
Vol 70 (02) ◽  
pp. 301-306 ◽  
Author(s):  
Linda A Robbie ◽  
Nuala A Booth ◽  
Alison M Croll ◽  
Bruce Bennett
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Fibrin Clot ◽  
Clot Lysis ◽  
Plasminogen Activator Inhibitor 1 ◽  
Dependent Inhibition ◽  
Activator Inhibitor ◽  
Pai 1

SummaryThe relative importance of the two major inhibitors of fibrinolysis, α2-antiplasmin (α2-AP) and plasminogen activator inhibitor (PAI-1), were investigated using a simple microtitre plate system to study fibrin clot lysis in vitro. Cross-linked fibrin clots contained plasminogen and tissue plasminogen activator (t-PA) at concentrations close to physiological. Purified α2-AP and PAI-1 caused dose-dependent inhibition. All the inhibition due to normal plasma, either platelet-rich or poor, was neutralised only by antibodies to α2-AP. Isolated platelets, at a final concentration similar to that in blood, 2.5 × 108/ml, markedly inhibited clot lysis. This inhibition was neutralised only by antibodies to PAI-1. At the normal circulating ratio of plasma to platelets, α2-AP was the dominant inhibitor. When the platelet:plasma ratio was raised some 20-fold, platelet PAI-1 provided a significant contribution. High local concentrations of PAI-1 do occur in thrombi in vivo, indicating a role for PAI-1, complementary to that of α2-AP, in such situations.

scholarly journals Role of plasminogen activator inhibitor-1 in promoting fibrin deposition in rabbits infused with ancrod or thrombin

Blood ◽  
1993 ◽  
Vol 82 (12) ◽  
pp. 3631-3636 ◽  
Author(s):  
C Krishnamurti ◽  
C Bolan ◽  
CA Colleton ◽  
TM Reilly ◽  
BM Alving
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Fibrin Deposition ◽  
Plasminogen Activator Inhibitor 1 ◽  
Elevated Activity ◽  
Activator Inhibitor ◽  
Pai 1

The role of defective fibrinolysis caused by elevated activity of plasminogen activator inhibitor-1 (PAI-1) in promoting fibrin deposition in vivo has not been well established. The present study compared the efficacy of thrombin or ancrod, a venom-derived enzyme that clots fibrinogen, to induce fibrin formation in rabbits with elevated PAI-1 levels. One set of male New Zealand rabbits received intravenous endotoxin to increase endogenous PAI-1 activity followed by a 1-hour infusion of ancrod or thrombin; another set of normal rabbits received intravenous human recombinant PAI-1 (rPAI-1) during an infusion of ancrod or thrombin. Thirty minutes after the end of the infusion, renal fibrin deposition was assessed by histopathology. Animals receiving endotoxin, rPAI-1, ancrod, or thrombin alone did not develop renal thrombi. All endotoxin-treated rabbits developed fibrin deposition when infused with ancrod (n = 4) or thrombin (n = 6). Fibrin deposition occurred in 7 of 7 rabbits receiving both rPAI-1 and ancrod and in only 1 of 6 receiving rPAI-1 and thrombin (P “ .01). In vitro, thrombin but not ancrod was inactivated by normal rabbit plasma and by purified antithrombin III or thrombomodulin. The data indicate that elevated levels of PAI-1 promote fibrin deposition in rabbits infused with ancrod but not with thrombin. In endotoxin-treated rabbits, fibrin deposition that occurs with thrombin infusion may be caused by decreased inhibition of procoagulant activity and not increased PAI-1 activity.

scholarly journals Role of plasminogen activator inhibitor-1 in promoting fibrin deposition in rabbits infused with ancrod or thrombin

Blood ◽  
1993 ◽  
Vol 82 (12) ◽  
pp. 3631-3636 ◽  
Author(s):  
C Krishnamurti ◽  
C Bolan ◽  
CA Colleton ◽  
TM Reilly ◽  
BM Alving
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Fibrin Deposition ◽  
Plasminogen Activator Inhibitor 1 ◽  
Elevated Activity ◽  
Activator Inhibitor ◽  
Pai 1

Abstract The role of defective fibrinolysis caused by elevated activity of plasminogen activator inhibitor-1 (PAI-1) in promoting fibrin deposition in vivo has not been well established. The present study compared the efficacy of thrombin or ancrod, a venom-derived enzyme that clots fibrinogen, to induce fibrin formation in rabbits with elevated PAI-1 levels. One set of male New Zealand rabbits received intravenous endotoxin to increase endogenous PAI-1 activity followed by a 1-hour infusion of ancrod or thrombin; another set of normal rabbits received intravenous human recombinant PAI-1 (rPAI-1) during an infusion of ancrod or thrombin. Thirty minutes after the end of the infusion, renal fibrin deposition was assessed by histopathology. Animals receiving endotoxin, rPAI-1, ancrod, or thrombin alone did not develop renal thrombi. All endotoxin-treated rabbits developed fibrin deposition when infused with ancrod (n = 4) or thrombin (n = 6). Fibrin deposition occurred in 7 of 7 rabbits receiving both rPAI-1 and ancrod and in only 1 of 6 receiving rPAI-1 and thrombin (P “ .01). In vitro, thrombin but not ancrod was inactivated by normal rabbit plasma and by purified antithrombin III or thrombomodulin. The data indicate that elevated levels of PAI-1 promote fibrin deposition in rabbits infused with ancrod but not with thrombin. In endotoxin-treated rabbits, fibrin deposition that occurs with thrombin infusion may be caused by decreased inhibition of procoagulant activity and not increased PAI-1 activity.

scholarly journals Inhibition of clot lysis and decreased binding of tissue-type plasminogen activator as a consequence of clot retraction

Blood ◽  
1992 ◽  
Vol 79 (6) ◽  
pp. 1420-1427 ◽  
Author(s):  
S Kunitada ◽  
GA FitzGerald ◽  
DJ Fitzgerald
Keyword(s):  
Plasminogen Activator ◽  
Tissue Type ◽  
Clot Lysis ◽  
Plasminogen Activator Inhibitor 1 ◽  
Clot Retraction ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator ◽  
Pai 1

Tissue-type plasminogen activator (t-PA) is less active in vivo and in vitro against clots that are enriched in platelets, even at therapeutic concentrations. The release of radioactivity from 125I-fibrin-labeled clots was decreased by 47% 6 hours after the addition of t-PA 400 U/mL when formed in platelet-rich versus platelet-poor plasma. This difference was not due to the release of plasminogen activator inhibitor-1 (PAI-1) by platelets. Thus, the fibrinolytic activity of t- PA in the supernatant was similar in the two preparations and fibrin autography demonstrated only a minor degree of t-PA-PAI-1 complex formation. Furthermore, a similar platelet-dependent reduction in clot lysis was seen with a t-PA mutant resistant to inhibition by PAI-1. The reduction in t-PA activity correlated with a decrease in t-PA binding to platelet-enriched clot (60% +/- 3% v platelet-poor clot, n = 5). This reduction in binding was also shown using t-PA treated with the chloromethylketone, D-Phe-Pro-Arg-CH2Cl (PPACK) (36% +/- 13%, n = 3), and with S478A, a mutant t-PA in which the active site serine at position 478 has been substituted by alanine (43% +/- 6%, n = 3). In contrast, fixed platelets and platelet supernatants had no effect on the binding or lytic activity of t-PA. Pretreatment with cytochalasin D 1 mumol/L, which inhibits clot retraction, also abolished the platelet- induced inhibition of lysis and t-PA binding by platelets. These data suggest that platelets inhibit clot lysis at therapeutic concentrations of t-PA as a consequence of clot retraction and decreased access of fibrinolytic proteins.

Reactivated Recombinant Plasminogen Activator Inhibitor-1 (rPAI-1) Effectively Prevents Thrombolysis In Vivo

1992 ◽  
Vol 68 (01) ◽  
pp. 060-063 ◽  
Author(s):  
Douglas E Vaughan ◽  
Paul J Declerck ◽  
Elizabeth Van Houtte ◽  
Maria De Mol ◽  
Désiré Collen
Keyword(s):  
Plasminogen Activator ◽  
Rabbit Model ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
Clot Lysis ◽  
Plasminogen Activator Inhibitor 1 ◽  
Jugular Vein Thrombosis ◽  
Activator Inhibitor ◽  
Pai 1

SummaryThe effects of human recombinant plasminogen activator inhibitor (rPAI-1) on thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) were studied in a rabbit model of jugular vein thrombosis. Two functionally distinct rPAI-1 preparations were used in these experiments, including latent rPAI-1 (~2 units of t-PA neutralizing activity per µg protein) and reactivated rPAI-1 (~150 units/µg).Simultaneous intravenous infusion over 4 h of 1.7 mg/kg of reactivated rPAI-1 (inhibitory capacity ~0.5 mg/kg rt-PA) with 0.5 mg/kg of rt-PA completely prevented lysis of a jugular venous thrombus, whereas an equivalent amount of latent PAI-1 did not significantly influence clot lysis. These findings demonstrate that reactivated human rPAI-1 efficiently neutralizes thrombolysis with rt-PA in vivo. Since previous studies have suggested that elevated endogenous levels of PAI-1 do not attenuate the thrombolytic potency of rt-PA in the endotoxin-treated model, we compared the stability of complexes formed by 125I-rt-PA with reactivated human rPAI-1 and with rabbit PAI-1 in vitro. Our findings indicate that both forms of PAI-1 form SDS-stable complexes following incubation with 125I-rt-PA. Thus, it seems likely that elevated levels of active PAI-1 can negate the thrombolytic effects of rt-PA in vivo and argues against the possibility that t-PA can dissociate from PAI-1 and have its activity restored in the presence of a thrombus. We propose that the present model may be a valuable tool in monitoring and evaluating the in vivo thrombolytic efficacy of various t-PA mutants designed to be less sensitive to the inhibitory effects of PAI-1.

Impairment of adipose tissue development by hypoxia is not mediated by plasminogen activator inhibitor-1

2006 ◽  
Vol 95 (01) ◽  
pp. 174-181 ◽  
Author(s):  
Fabrizio Semeraro ◽  
Gabor Voros ◽  
Désiré Collen ◽  
H. Lijnen
Keyword(s):  
Adipose Tissue ◽  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Development ◽  
Plasminogen Activator Inhibitor 1 ◽  
Adipose Tissue Development ◽  
Activator Inhibitor ◽  
Pai 1

SummaryHypoxia in rodents and humans is associated with a reduction of body fat on the one hand, and with enhanced expression of plasminogen activator inhibitor-1 (PAI-1), the main inhibitor of the fibrinolytic system, on the other hand. It was the objective of this study to investigate whether impairment of adipose tissue development by hypoxia may be mediated by PAI-1. Five week old male wild-type (WT) C57Bl/6 mice were fed a standard (SFD) or high fat (HFD) diet and kept under normoxic or hypoxic (10% O2) conditions. In addition, PAI-1 deficient mice and WT littermates were kept on HFD under normoxia or hypoxia. In vitro, the effect of hypoxia (2% O2) was investigated on differentiation of 3T3-L1 cells into adipocytes. Hypoxia induced a significant reduction of weight gain in WT mice on either SFD or HFD, accompanied by lower weights of subcutaneous (SC) and gonadal (GON) fat. Under hypoxic conditions, adipocytes in the adipose tissues were significantly smaller, whereas blood vessel size and density were larger. Serum PAI-1 levels were enhanced in hypoxic mice on SFD but not on HFD, and overall did not correlate with the observed changes in adipose tissue composition. Furthermore, the effects of hypoxia on adipose tissue in mice on HFD were not affected by deficiency of PAI-1. The inhibiting effect of hypoxia on in vitro preadipocyte differentiation was not mediated by PAI-1 activity. In conclusion, impairment of in vivo adipose tissue development and in vitro differentiation of preadipocytes by hypoxia is not mediated by PAI-1.

scholarly journals PAI-1-resistant t-PA: low doses prevent fibrin deposition in rabbits with increased PAI-1 activity

Blood ◽  
1996 ◽  
Vol 87 (1) ◽  
pp. 14-19
Author(s):  
C Krishnamurti ◽  
B Keyt ◽  
P Maglasang ◽  
BM Alving
Keyword(s):  
Plasminogen Activator ◽  
Low Dose ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
Fibrin Deposition ◽  
Plasminogen Activator Inhibitor 1 ◽  
Resistant Variant ◽  
Type Plasminogen Activator ◽  
Pai 1

The present study compared the activities of recombinant tissue-type plasminogen activator (t-PA) and a plasminogen activator inhibitor-1 (PAI-1)-resistant variant t-PA (Kt-PA, KHRR 296–299 AAAA) in preventing renal fibrin deposition in rabbits with elevated PAI-1 activity. In this model, all rabbits were infused with endotoxin (10 micrograms/kg), followed by initiation of thrombin (130 U/kg) 4 hours later, when plasma PAI-1 activity was greater than 200 arbitrary units (AU)/mL (baseline, < 3 AU/mL). Thirty minutes after completion of the 1-hour thrombin infusion, rabbits were killed and the kidneys fixed and stained for identification of fibrin deposition. Rabbits received one of the following treatments initiated 30 minutes before thrombin and continued during the 1-hour thrombin infusion: (1) saline (n = 7); (2) low-dose t-PA (17 micrograms/kg, n = 4); (3) higher-dose t-PA (170 micrograms/kg, n = 4); or (4) low-dose Kt-PA (17 micrograms/kg, n = 6). Fibrin deposition occurred in 86% and 100% of the rabbits receiving saline or low-dose t-PA, respectively. Fibrin deposition did not occur in any of the rabbits receiving low-dose Kt-PA or higher-dose t-PA. Low-dose Kt-PA and higher dose t-PA also caused a reduction in fibrin deposition when infused after thrombin administration had been completed. The data provide in vivo evidence that Kt-PA is more effective than t-PA in preventing fibrin deposition in an animal model that combines thrombogenic stimulation with increased PAI-1 activity.

Generation and in vitro characterisation of inhibitory nanobodies towards plasminogen activator inhibitor 1

2016 ◽  
Vol 116 (12) ◽  
pp. 1032-1040 ◽  
Author(s):  
Xiaohua Zhou ◽  
Maarten L. V. Hendrickx ◽  
Gholamreza Hassanzadeh-Ghassabeh ◽  
Serge Muyldermans ◽  
Paul J. Declerck
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Hinge Region ◽  
Tissue Type ◽  
Clot Lysis ◽  
Plasminogen Activator Inhibitor 1 ◽  
Type Plasminogen Activator ◽  
Activator Inhibitor ◽  
Pai 1

SummaryPlasminogen activator inhibitor 1 (PAI-1) is the principal physiological inhibitor of tissue-type plasminogen activator (t-PA) and has been identified as a risk factor in cardiovascular diseases. In order to generate nanobodies against PAI-1 to interfere with its functional properties, we constructed three nanobody libraries upon immunisation of three alpacas with three different PAI-1 variants. Three panels of nanobodies were selected against these PAI-1 variants. Evaluation of the amino acid sequence identity of the complementarity determining region-3 (CDR3) reveals 34 clusters in total. Five nanobodies (VHH-s-a98, VHH-2w-64, VHH-s-a27, VHH-s-a93 and VHH-2g-42) representing five clusters exhibit inhibition towards PAI-1 activity. VHH-s-a98 and VHH-2w-64 inhibit both glycosylated and non-glycosylated PAI-1 variants through a substrate-inducing mechanism, and bind to two different regions close to αhC and the hinge region of αhF; the profibrinolytic effect of both nanobodies was confirmed using an in vitro clot lysis assay. VHH-s-a93 may inhibit PAI-1 activity by preventing the formation of the initial PAI-1•t-PA complex formation and binds to the hinge region of the reactive centre loop. Epitopes of VHH-s-a27 and VHH-2g-42 could not be deduced yet. These five nanobodies interfere with PAI-1 activity through different mechanisms and merit further evaluation for the development of future profibrinolytic therapeutics.

Inhibitor-Resistant Tissue-Type Plasminogen Activator: An Improved Thrombolytic Agent In Vitro

1994 ◽  
Vol 71 (01) ◽  
pp. 124-128 ◽  
Author(s):  
R V Shohet ◽  
S Spitzer ◽  
E L Madison ◽  
R Bassel-Duby ◽  
M-J Gething ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
Wild Type ◽  
Plasminogen Activator Inhibitor 1 ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator ◽  
Pai 1

SummaryPlatelet-rich clots are inefficiently lysed by current fibrinolytic agents. Platelets contain a great deal of plasminogen activator inhibitor 1 (PAI-1), the principal endogenous inhibitor of tissue-type plasminogen activator (t-PA). We have tested whether PAI-1 resistant t-PAs would be more effective thrombolytic agents in an in vitro model of platelet rich clots. Clots were formed with recalcified human plasma without or with the addition of platelets. The lysis of these clots was followed by the release of incorporated 125I-fibrinogen. Mutant and wild-type t-PA were almost equally effective against clots lacking platelets but the mutant was twice as effective at lysing platelet-rich clots. A mechanism for this effect is suggested by the demonstration that a complex between wild-type t-PA and extruded platelet contents resembles that between purified t-PA and PAI-1 and that the PAI-1 resistant t-PA does not interfere with formation of this adduct. Because of its enhanced ability to lyse platelet-rich clots in vitro, further in vivo work may find that PAI-1 resistant t-PA is a more efficacious therapeutic agent than wild-type t-PA in situations where platelets contribute to the failure of thrombolysis.

scholarly journals PAI-1-resistant t-PA: low doses prevent fibrin deposition in rabbits with increased PAI-1 activity

Blood ◽  
1996 ◽  
Vol 87 (1) ◽  
pp. 14-19 ◽  
Author(s):  
C Krishnamurti ◽  
B Keyt ◽  
P Maglasang ◽  
BM Alving
Keyword(s):  
Plasminogen Activator ◽  
Low Dose ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
Fibrin Deposition ◽  
Plasminogen Activator Inhibitor 1 ◽  
Resistant Variant ◽  
Type Plasminogen Activator ◽  
Pai 1

Abstract The present study compared the activities of recombinant tissue-type plasminogen activator (t-PA) and a plasminogen activator inhibitor-1 (PAI-1)-resistant variant t-PA (Kt-PA, KHRR 296–299 AAAA) in preventing renal fibrin deposition in rabbits with elevated PAI-1 activity. In this model, all rabbits were infused with endotoxin (10 micrograms/kg), followed by initiation of thrombin (130 U/kg) 4 hours later, when plasma PAI-1 activity was greater than 200 arbitrary units (AU)/mL (baseline, < 3 AU/mL). Thirty minutes after completion of the 1-hour thrombin infusion, rabbits were killed and the kidneys fixed and stained for identification of fibrin deposition. Rabbits received one of the following treatments initiated 30 minutes before thrombin and continued during the 1-hour thrombin infusion: (1) saline (n = 7); (2) low-dose t-PA (17 micrograms/kg, n = 4); (3) higher-dose t-PA (170 micrograms/kg, n = 4); or (4) low-dose Kt-PA (17 micrograms/kg, n = 6). Fibrin deposition occurred in 86% and 100% of the rabbits receiving saline or low-dose t-PA, respectively. Fibrin deposition did not occur in any of the rabbits receiving low-dose Kt-PA or higher-dose t-PA. Low-dose Kt-PA and higher dose t-PA also caused a reduction in fibrin deposition when infused after thrombin administration had been completed. The data provide in vivo evidence that Kt-PA is more effective than t-PA in preventing fibrin deposition in an animal model that combines thrombogenic stimulation with increased PAI-1 activity.

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