scholarly journals Pharmacokinetics and thrombolytic properties of deletion mutants of human tissue-type plasminogen activator in rabbits

Blood ◽  
1988 ◽  
Vol 71 (1) ◽  
pp. 216-219
Author(s):  
D Collen ◽  
JM Stassen ◽  
G Larsen
Keyword(s):  
Plasminogen Activator ◽  
Human Tissue ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Tissue Type ◽  
Jugular Vein Thrombosis ◽  
Thrombolytic Activity ◽  
Tissue Type Plasminogen Activator ◽  
Deletion Mutagenesis ◽  
Type Plasminogen Activator

The following mutants of human tissue-type plasminogen activator (t-PA) were constructed by deletion mutagenesis of t-PA cDNA, expressed in Chinese hamster ovary cells and purified to homogeneity: (a) t-PA-delta FE:t-PA lacking both the fibronectin fingerlike (F) domain and the epidermal growth factor (E) domain, (b) t-PA-delta FE1X:t-PA-delta FE with the glycosylated 117Asn mutagenized to Gln, and (c) t-PA-delta FE3X:t-PA-delta FE with the three known glycosylated Asn residues replaced by Gln. The mutant and natural t-PA (Mel-t-PA obtained from melanoma cell culture) were infused intravenously for four hours into rabbits with jugular vein thrombosis at doses ranging between 0.12 and 0.75 mg/kg. Fifty percent thrombolysis, determined by interpolation, was obtained with 0.4 mg/kg Mel-t-PA, 0.37 mg/kg t-PA-delta FE, 0.2 mg/kg t-PA-delta FE1X, and 0.40 mg/kg t-PA-delta FE3X. These infusion rates resulted in plateau levels of t-PA antigen in plasma of 0.055, 2.1, 0.6, and 0.5 micrograms/mL, respectively. At 50% lysis, the residual fibrinogen 30 minutes after the end of the infusion was 100%, 81%, 100% and 85% of baseline, and the residual alpha 2-antiplasmin was 82%, 55%, 85%, and 90%, respectively. These results indicate that t-PA- delta FE1X and t-PA-delta FE3X have a specific thrombolytic activity and fibrin specificity comparable to that of Mel-t-PA. t-PA-delta FE has a comparable specific thrombolytic activity but a lower fibrin specificity than Mel-t-PA. After the end of the infusion, t-PA-related antigen disappeared from plasma with an initial t1/2 of four minutes for Mel-t-PA, 25 minutes for t-PA-delta FE, 42 minutes for t-PA-delta FE1X, and 14 minutes for t-PA-delta FE3X. It is concluded that t-PA can be modified by deletion mutagenesis to yield variants with a markedly longer half-life in the blood. Some of these variants have a specific thrombolytic activity and fibrin specificity similar to that of natural t-PA. These variants may be useful to identify the structures in t-PA responsible for its clearance, specific thrombolytic activity, and fibrin specificity in vivo.

scholarly journals Pharmacokinetics and thrombolytic properties of deletion mutants of human tissue-type plasminogen activator in rabbits

Blood ◽  
1988 ◽  
Vol 71 (1) ◽  
pp. 216-219 ◽  
Author(s):  
D Collen ◽  
JM Stassen ◽  
G Larsen
Keyword(s):  
Plasminogen Activator ◽  
Human Tissue ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Tissue Type ◽  
Jugular Vein Thrombosis ◽  
Thrombolytic Activity ◽  
Tissue Type Plasminogen Activator ◽  
Deletion Mutagenesis ◽  
Type Plasminogen Activator

Abstract The following mutants of human tissue-type plasminogen activator (t-PA) were constructed by deletion mutagenesis of t-PA cDNA, expressed in Chinese hamster ovary cells and purified to homogeneity: (a) t-PA-delta FE:t-PA lacking both the fibronectin fingerlike (F) domain and the epidermal growth factor (E) domain, (b) t-PA-delta FE1X:t-PA-delta FE with the glycosylated 117Asn mutagenized to Gln, and (c) t-PA-delta FE3X:t-PA-delta FE with the three known glycosylated Asn residues replaced by Gln. The mutant and natural t-PA (Mel-t-PA obtained from melanoma cell culture) were infused intravenously for four hours into rabbits with jugular vein thrombosis at doses ranging between 0.12 and 0.75 mg/kg. Fifty percent thrombolysis, determined by interpolation, was obtained with 0.4 mg/kg Mel-t-PA, 0.37 mg/kg t-PA-delta FE, 0.2 mg/kg t-PA-delta FE1X, and 0.40 mg/kg t-PA-delta FE3X. These infusion rates resulted in plateau levels of t-PA antigen in plasma of 0.055, 2.1, 0.6, and 0.5 micrograms/mL, respectively. At 50% lysis, the residual fibrinogen 30 minutes after the end of the infusion was 100%, 81%, 100% and 85% of baseline, and the residual alpha 2-antiplasmin was 82%, 55%, 85%, and 90%, respectively. These results indicate that t-PA- delta FE1X and t-PA-delta FE3X have a specific thrombolytic activity and fibrin specificity comparable to that of Mel-t-PA. t-PA-delta FE has a comparable specific thrombolytic activity but a lower fibrin specificity than Mel-t-PA. After the end of the infusion, t-PA-related antigen disappeared from plasma with an initial t1/2 of four minutes for Mel-t-PA, 25 minutes for t-PA-delta FE, 42 minutes for t-PA-delta FE1X, and 14 minutes for t-PA-delta FE3X. It is concluded that t-PA can be modified by deletion mutagenesis to yield variants with a markedly longer half-life in the blood. Some of these variants have a specific thrombolytic activity and fibrin specificity similar to that of natural t-PA. These variants may be useful to identify the structures in t-PA responsible for its clearance, specific thrombolytic activity, and fibrin specificity in vivo.

Coamplification and coexpression of human tissue-type plasminogen activator and murine dihydrofolate reductase sequences in Chinese hamster ovary cells

1985 ◽  
Vol 5 (7) ◽  
pp. 1750-1759
Author(s):  
R J Kaufman ◽  
L C Wasley ◽  
A J Spiliotes ◽  
S D Gossels ◽  
S A Latt ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Dihydrofolate Reductase ◽  
Chinese Hamster Ovary ◽  
Human Tissue ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Tissue Type ◽  
Expression Vectors ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator

Expression of human tissue-type plasminogen activator (t-PA) at high levels has been achieved in Chinese hamster ovary (CHO) cells by cotransfection and subsequent coamplification of the transfected sequences. Expression vectors containing the t-PA cDNA gene and dihydrofolate reductase (DHFR) cDNA gene were cotransfected into CHO DHFR-deficient cells. Transformants expressing DHFR were selected by growth in media lacking nucleosides and contained low numbers of t-PA genes and DHFR genes. Stepwise selection of the DHFR+ transformants in increasing concentrations of methotrexate generated cells which had amplified both DHFR genes and t-PA genes over 100-fold. These cell lines expressed elevated levels of enzymatically active t-PA. To optimize both t-PA sequence amplification and t-PA expression, various modifications of the original procedure were used. These included alterations to the DHFR expression vector, optimization of the molar ratio of t-PA to DHFR sequences in the cotransfection, and modification of the methotrexate resistance selection procedure. The structure of the amplified DNA, its chromosomal location, and its stability during growth in the absence of methotrexate are reported.

scholarly journals Coamplification and coexpression of human tissue-type plasminogen activator and murine dihydrofolate reductase sequences in Chinese hamster ovary cells.

1985 ◽  
Vol 5 (7) ◽  
pp. 1750-1759 ◽  
Author(s):  
R J Kaufman ◽  
L C Wasley ◽  
A J Spiliotes ◽  
S D Gossels ◽  
S A Latt ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Dihydrofolate Reductase ◽  
Chinese Hamster Ovary ◽  
Human Tissue ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Tissue Type ◽  
Expression Vectors ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator

Expression of human tissue-type plasminogen activator (t-PA) at high levels has been achieved in Chinese hamster ovary (CHO) cells by cotransfection and subsequent coamplification of the transfected sequences. Expression vectors containing the t-PA cDNA gene and dihydrofolate reductase (DHFR) cDNA gene were cotransfected into CHO DHFR-deficient cells. Transformants expressing DHFR were selected by growth in media lacking nucleosides and contained low numbers of t-PA genes and DHFR genes. Stepwise selection of the DHFR+ transformants in increasing concentrations of methotrexate generated cells which had amplified both DHFR genes and t-PA genes over 100-fold. These cell lines expressed elevated levels of enzymatically active t-PA. To optimize both t-PA sequence amplification and t-PA expression, various modifications of the original procedure were used. These included alterations to the DHFR expression vector, optimization of the molar ratio of t-PA to DHFR sequences in the cotransfection, and modification of the methotrexate resistance selection procedure. The structure of the amplified DNA, its chromosomal location, and its stability during growth in the absence of methotrexate are reported.

Thrombolytic Treatment with Tissue-type Plasminogen Activator (t-PA) Containing Liposomes in Rabbits: a Comparison with Free t-PA

1995 ◽  
Vol 73 (03) ◽  
pp. 488-494 ◽  
Author(s):  
J L M Heeremans ◽  
R Prevost ◽  
M E A Bekkers ◽  
P Los ◽  
J J Emeis ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Therapeutic Index ◽  
Tissue Type ◽  
Jugular Vein Thrombosis ◽  
Thrombolytic Activity ◽  
Tissue Type Plasminogen Activator ◽  
Liposome Encapsulation ◽  
Thrombosis Model ◽  
Lysis Activity ◽  
Type Plasminogen Activator

SummaryIn this study, we aimed at improving the therapeutic index of tissue- type Plasminogen Activator (t-PA) as thrombolytic agent in the treatment of myocardial infarction. Liposome-encapsulated t-PA was tested in a rabbit jugular vein thrombosis model: administration of free t-PA (t-PA) as a bolus injection in the ear vein was compared to a similar administration of liposomal t-PA (t-PA-lip), liposomal t-PA in plasminogen-coated liposomes (Plg-t-PA-lip), a mixture of free t-PA and empty liposomes (t-PA+empty lip) and a saline-blank (blank) in terms of thrombolytic activity and side effects.Liposomal t-PA (t-PA-lip/Plg-t-PA-lip) showed a significantly better thrombolysis efficiency than equimolar doses of free t-PA (t-PA/ t-PA+ empty lip): about 0.24 mg/kg of liposomal t-PA practically equalled the lysis-activity of a dose of free t-PA of 1.0 mg/kg (t-PAlmg/kg). On the other hand, liposome encapsulation did not affect the systemic activation of alpha2-antiplasmin and plasminogen by t-PA.We conclude that for this model an improvement in thrombolytic efficacy of t-PA is achieved by liposome encapsulation of t-PA. As t-PA-lip and Plg-t-PA-lip -treatment induced similar results, targeting of liposomal t-PA by coupled glu-Plg remains a topic to be optimized in future studies.

Sign in / Sign up

Export Citation Format

Share Document