Abstract 172: tPA Variant tPA-A296-299 Prevents Impairment of Cerebral Autoregulation After Stroke Through LRP Dependent Increase in cAMP and p38 MAPK

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
William Armstead ◽  
John Riley ◽  
Serge Yarovoi ◽  
Abd Al-Roof Higazi ◽  
Douglas Cines
Keyword(s):  
Cerebral Autoregulation ◽  
Tissue Type ◽  
Therapeutic Window ◽  
Wild Type ◽  
Tissue Type Plasminogen Activator ◽  
P38 Inhibitor ◽  
Cranial Window ◽  
Limited Efficacy ◽  
Type Plasminogen Activator ◽  
Sb 203580

Introduction: The sole FDA approved treatment for acute stroke is tissue type plasminogen activator (tPA). However, its brief therapeutic window and post-treatment complications markedly constrain its use. The limited efficacy of tPA may be explained in part by our finding that it potentiates impairment of cerebral autoregulation after stroke in pigs. Upregulation of JNK MAPK after thrombotic stroke contributes to tPA mediated impairment of autoregulation whereas p38 is protective. Vasodilation is mediated by elevation of cAMP. However, cAMP falls after stroke due to over activation of NMDA receptors (NMDA-Rs) by toxic levels of glutamate, which is exacerbated by tPA. Hypothesis: Wild type (wt) tPA can bind to either the lipoprotein-related receptor (LRP), which mediates vasodilation, or NMDA-Rs. We propose that wt tPA given after stroke primarily binds to NMDA-Rs, reduces cAMP, which impairs ability of cerebral vessels to vasodilate. tPA-A296-299, a variant that is fibrinolytic but cannot bind to NMDA-Rs, preferentially binds LRP, which increases cAMP and p38 and limits impairment of autoregulation after stroke. Methods: Anesthetized pigs equipped with a closed cranial window were used. Stroke was induced by photothrombosis, CBF determined by radiolabeled microspheres, and CSF cAMP and p38 determined by ELISA. Results: CBF was unchanged during hypotension (mean arterial pressure decreased by 45%) in sham animals. CBF was reduced in brain tissue surrounding the infarct and was reduced further during hypotension, indicating impairment of autoregulation. Autoregulation was further impaired by wt tPA which was prevented by MK801 and tPA-A296-299. Protection by tPA-A296-299 was blocked by anti LRP Ab, the LRP antagonist RAP, the p38 inhibitor SB 203580, but not by IgG. Stroke reduced CSF cAMP, which was reduced further by wt tPA, but augmented by tPA-A296-299. CSF p38 was unchanged by wt tPA, robustly increased by tPA-A296-299, and decreased by co-administered anti LRP Ab and RAP but not by IgG. Conclusions: tPA-A296-299 prevents impairment of cerebral autoregulation after stroke through LRP dependent increase in cAMP and p38.

Abstract WP285: tPA Variant tPA-A296-299 Prevents Impairment of Cerebral Autoregulation and Hippocampal Neuronal Necrosis After Stroke Through Inhibition of ET-1 Upregulation

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
William Armstead ◽  
Hugh Hekierski ◽  
Serge Yarovoi ◽  
Abd Al-Roof Higazi ◽  
Douglas Cines
Keyword(s):  
Cerebral Autoregulation ◽  
Neuronal Cell ◽  
Tissue Type ◽  
Therapeutic Window ◽  
Dependent Manner ◽  
Wild Type ◽  
Neuronal Necrosis ◽  
Cranial Window ◽  
Type Plasminogen Activator

Introduction: The sole FDA approved treatment for acute stroke is tissue type plasminogen activator (tPA). However, its brief therapeutic window and post-treatment complications markedly constrain its use. The limited efficacy of tPA may be explained in part by our finding that it potentiates impairment of cerebral autoregulation after stroke in pigs. Upregulation of JNK MAPK after thrombotic stroke contributes to tPA mediated impairment of autoregulation. However, the role of ET-1, and its relationship to JNK, in impairment of autoregulation is unknown. Impairment of autoregulation is linked to Glasgow Coma Scale after brain injury, but unknown if autoregulation correlates with hippocampal histopathology after stroke. Hypothesis: Wild type (wt) tPA can bind to either the lipoprotein-related receptor (LRP), which mediates vasodilation, or NMDA-Rs. We propose that wt tPA given after stroke primarily binds to NMDA-Rs, upregulates ET-1 in a JNK dependent manner, which impairs autoregulation, causing histopathology. tPA-A 296-299 , a variant that is fibrinolytic but cannot bind to NMDA-Rs, preferentially binds LRP, which blocks ET-1 and JNK upregulation and limits impairment of autoregulation and histopathology after stroke. Methods: Anesthetized pigs equipped with a closed cranial window were used. Stroke was induced by photothrombosis, CBF determined by radiolabeled microspheres, CSF ET-1 and JNK determined by ELISA and histopathology determined with H + E stain. Results: CBF was unchanged during hypotension (mean arterial pressure decreased by 45%) in sham animals. CBF was reduced in brain tissue surrounding the infarct and was reduced further during hypotension, indicating impairment of autoregulation. CA1 and CA3 neuronal cell necrosis and autoregulation were further impaired by wt tPA which was prevented by BQ 123 and tPA-A 296-299 . Cerebral ET-1 was increased by stroke, potentiated by wt tPA, but returned to sham baseline value by tPA-A 296-299 and the JNK antagonist SP600125. Conclusions: JNK contributes to ET-1 release after stroke. tPA-A 296-299 prevents impairment of cerebral autoregulation and histopathology after stroke through inhibition of ET-1 upregulation.

Recombinant Variants of Tissue-Type Plasminogen Activator Containing Amino Acid Substitutions in the Finger Domain

1992 ◽  
Vol 68 (06) ◽  
pp. 672-677 ◽  
Author(s):  
Hitoshi Yahara ◽  
Keiji Matsumoto ◽  
Hiroyuki Maruyama ◽  
Tetsuya Nagaoka ◽  
Yasuhiro Ikenaka ◽  
...  
Keyword(s):  
Amino Acid ◽  
Plasminogen Activator ◽  
Half Life ◽  
Tissue Type ◽  
Clot Lysis ◽  
Amino Acid Substitutions ◽  
Wild Type ◽  
Plasma Clot ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator

SummaryTissue-type plasminogen activator (t-PA) is a fibrin-specific agent which has been used to treat acute myocardial infarction. In an attempt to clarify the determinants for its rapid clearance in vivo and high affinity for fibrin clots, we produced five variants containing amino acid substitutions in the finger domain, at amino acid residues 7–9, 10–14, 15–19, 28–33, and 37–42. All the variants had a prolonged half-life and a decreased affinity for fibrin of various degrees. The 37–42 variant demonstrated about a 6-fold longer half-life with a lower affinity for fibrin. Human plasma clot lysis assay estimated the fibrinolytic activity of the 37–42 variant to be 1.4-fold less effective than that of the wild-type rt-PA. In a rabbit jugular vein clot lysis model, doses of 1.0 and 0.15 mg/kg were required for about 70% lysis in the wild-type and 37–42 variant, respectively. Fibrinogen was degraded only when the wild-type rt-PA was administered at a dose of 1.0 mg/kg. These findings suggest that the 37–42 variant can be employed at a lower dosage and that it is a more fibrin-specific thrombolytic agent than the wild-type rt-PA.

scholarly journals Pharmacokinetic and distribution analysis of variant forms of tissue- type plasminogen activator with prolonged clearance in rat

Blood ◽  
1989 ◽  
Vol 73 (7) ◽  
pp. 1842-1850
Author(s):  
GR Larsen ◽  
M Metzger ◽  
K Henson ◽  
Y Blue ◽  
P Horgan
Keyword(s):  
Plasminogen Activator ◽  
Alpha Phase ◽  
Tissue Type ◽  
Distribution Analysis ◽  
Wild Type ◽  
Tissue Type Plasminogen Activator ◽  
Glycosylation Sites ◽  
Type Plasminogen Activator ◽  
Primary Determinant ◽  
Rapid Clearance

Human tissue-type plasminogen activator (t-PA) is a glycoprotein used currently in thrombolytic therapy. Because of its rapid half-life (T1/2) of approximately five minutes, intravenous (IV) infusion of large doses (approximately 100 mg) are required in patients treated for myocardial infarction. To identify the determinant(s) on t-PA responsible for such rapid clearance, metabolically labeled forms of recombinant t-PA were analyzed in rats following IV administration. The following seven forms of t-PA were tested: (a) natural or glycosylated wild-type t-PA; (b) nonglycosylated wild-type t-PA; (c) delta F t-PA, which lacks the fibronectin fingerlike domain; (d) delta E t-PA, which lacks the epidermal growth factor (EGF) domain; (e) delta FE t-PA, which lacks both the finger and EGF domains; (f) delta FE3X t-PA, a form of delta FE t-PA in which Asn-linked glycosylation is prevented at all known glycosylation sites (Asn-117, 184, and 448; replaced by Gln); and (f) delta FE1X t-PA, a form of delta FE t-PA in which high-mannose- type glycosylation is prevented at Asn-117. Both glycosylated and nonglycosylated wild-type t-PA cleared in an exponential biphasic manner, with an initial alpha-phase T1/2 of 0.8 and 1.9 minutes, respectively. This result demonstrates that carbohydrate is not the primary mediator of the rapid clearance of t-PA. The liver was the primary organ responsible for uptake of these molecules. All other proteins tested, except for delta E t-PA, demonstrated primarily monophasic clearance patterns with T1/2 ranging between 12 and 27 minutes, and reduced uptake in the liver. delta E t-PA however, cleared in a biphasic manner with an alpha-phase T1/2 of 2.1 minutes. Results presented suggest that the clearance of t-PA is mediated by two distinct mechanisms. The primary determinant(s) responsible for modulating the rapid clearance of t-PA appears to be resident within the polypeptide sequence encoding the finger and/or EGF domains, with emphasis on the finger domain. A second and less significant contribution to clearance is defined by the presence and type of glycosylation.

scholarly journals PAI-1-derived peptide EEIIMD prevents impairment of cerebrovasodilation by augmenting p38 MAPK upregulation after cerebral hypoxia/ischemia

2010 ◽  
Vol 299 (1) ◽  
pp. H76-H80 ◽  
Author(s):  
William M. Armstead ◽  
John Riley ◽  
J. Willis Kiessling ◽  
Douglas B. Cines ◽  
Abd Al-Roof Higazi
Keyword(s):  
Plasminogen Activator ◽  
P38 Mapk ◽  
Plasminogen Activator Inhibitor ◽  
Tissue Type ◽  
Cerebral Hypoxia ◽  
Plasminogen Activator Inhibitor 1 ◽  
Cranial Window ◽  
Type Plasminogen Activator ◽  
Sb 203580 ◽  
Activator Inhibitor

Babies are frequently exposed to cerebral hypoxia and ischemia (H/I) during the perinatal period as a result of stroke, problems with delivery, or postdelivery respiratory management. The sole approved treatment for acute stroke is tissue type plasminogen activator. H/I impairs pial artery dilation (PAD) induced by hypercapnia and hypotension, the impairment aggravated by type plasminogen activator and attenuated by the plasminogen activator inhibitor-1-derived peptide EEIIMD. Mitogen-activated protein kinase (MAPK), a family of at least three kinases, ERK, p38, and JNK, is upregulated after H/I and ERK contribute to impaired cerebrovasodilation. This study determined the roles of p38 and JNK MAPK in the impairment of dilation post-H/I in pigs equipped with a closed cranial window and the relationship between alterations in MAPK isoforms and EEIIMD-mediated cerebrovascular protection. Cerebrospinal fluid-phosphorylated (activated) p38 MAPK, but not JNK MAPK, was increased after H/I, an effect potentiated by intravenous EEIIMD administered 1 h postinjury. PAD in response to hypercapnia and hypotension was blunted by H/I, but dilation was maintained by EEIIMD. PAD was further impaired by the p38 antagonist SB-203580 but unchanged by the JNK antagonist SP-600125. Isoproterenol-induced PAD was unchanged by H/I, EEIIMD, SB-203580, and SP-600125. These data indicate that postinjury treatment with EEIIMD attenuated impaired cerebrovasodilation post-H/I by upregulating p38 but not JNK. These data suggest that plasminogen activator inhibitor-1-based peptides and other approaches to upregulate p38 may offer a novel approach to increase the benefit-to-risk ratio of thrombolytic therapy for diverse central nervous system disorders associated with H/I.

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.

Recombinant Variants of Tissue-type Plasminogen Activator Containing Amino Acid Substitutions in the Fibronectin Finger-like Domain and the Kringle 1 Domain

1994 ◽  
Vol 72 (06) ◽  
pp. 893-899
Author(s):  
Hitoshi Yahara ◽  
Keiji Matsumoto ◽  
Hiroyuki Maruyama ◽  
Tetsuya Nagaoka ◽  
Yasuhiro Ikenaka ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Half Life ◽  
Bolus Injection ◽  
Tissue Type ◽  
Clot Lysis ◽  
Wild Type ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator ◽  
Plasma Half Life

SummaryTissue-type plasminogen activator (t-PA) is a fibrin-specific agent which is used to treat acute myocardial infarction. Pharmacokinetic-ally, t-PA is characterized by a rapid clearance from the circulation. In a previous study, we constructed variant forms of t-PA with genetic modifications at the fibronectin finger-like domain (finger domain) or at the kringle 1 domain (K1 domain). The finger modified variant, t-PA N37S.S38V.G39V.R40E. A41F.Q42S had about a 6.0-fold higher plasma half-life in vivo than wild-type t-PA. Two variants with modifications in the K1 domain, t-PA G161R.K162R.S165W and t-PA N115P, showed an improved kinetic parameters and a 2.2-fold higher plasma half-life in vivo than wild-type t-PA, respectively. To create a recombinant variant of t-PA with a higher enzymatic activity and a further prolonged half-life in vivo, the genes containing each modifications were joined and expressed in animal cells. The two variants, t-PA N37S.S38V G39V.R40E.A41F.Q42S.G161R.K162R.S165W and t-PA N37S.S38V.G39V.R40E.A41F.Q42S.N 115P, were purified from conditioned media and their biochemical, pharmacokinetic and thrombolytic profiles were investigated. Although the variant t-PA N37S.S38V.G39V.R40E.A41F.Q42S.G161R.K162R.S165W demonstrated an impaired enzymatic activity compared to the wild:type t-PA, the half-life of the variant, t-PA N37S.S38V.G39V.R40E.A41F.Q42S. N115P, following intravenous bolus injection in rabbits was considerably longer than that of finger-domain modified variants. Human plasma clot lysis assay estimated the fibrinolytic activity of both variants to be about 2.0-fold less effective than that of the wild-type t-PA. In the rabbit jugular vein clot lysis model, doses of 1.0 and 0.0625 mg/kg were required for about 70% lysis in the wild-type t-PA and t-PA N37S.S38V.G39V.R40E.A41F.Q42S.N115P, respectively. These findings suggested that the variant in this study can be used at a lower dosage in a single bolus injection.

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