Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.68 (tissue plasminogen activator)
11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently discovered that patients with essential hypertension have a markedly impaired capacity for stimulated release of tissue plasminogen activator (tPA) from vascular endothelium. This defect may reduce the chance of timely spontaneous thrombolysis in case of an atherothrombotic event. We now investigated whether increased intraluminal pressure as such may depress vascular tPA release or downregulate its gene expression. Segments of human umbilical veins were studied in a new computerized vascular perfusion model under steady laminar flow conditions for 3 or 6 hours. Paired segments were perfused at high or physiological intraluminal pressure (40 versus 20 mm Hg) under identical shear stress (10 dyne/cm(2)). Quantitative immunohistochemical evaluation of cellular tPA immunoreactivity was performed on paraffin-embedded 5-microm vascular sections. tPA mRNA in endothelial cells was quantified with reverse transcription real-time TaqMan polymerase chain reaction with GAPDH as endogenous control. Secretion of tPA into perfusion medium was evaluated with SDS-PAGE and Western blotting, followed by densitometric quantification. High-pressure perfusion downregulated tPA gene expression with a 38% decrease in tPA mRNA levels (P=0.01) compared with vessels perfused under normal intraluminal pressure. tPA release into the perfusion medium was markedly suppressed by high pressure (P<0.01 ANOVA). The intracellular storage pool of tPA was reduced after 6 but not 3 hours. Thus, elevated intraluminal pressure downregulates tPA gene and protein expression and inhibits its release from the endothelium independently of shear stress. The defective capacity for stimulated tPA release that we demonstrated in patients with essential hypertension might thus be an effect of the elevated intraluminal pressure per se.
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PMID:Elevated intraluminal pressure inhibits vascular tissue plasminogen activator secretion and downregulates its gene expression. 1077 76

We assessed forearm blood flow and plasma fibrinolytic factors in eight healthy males who received unilateral brachial artery infusions of the endothelium-dependent vasodilator, substance P, and the endothelium-independent vasodilator, sodium nitroprusside. These measurements, together with platelet aggregation studies, were performed on four occasions after double-blind randomized ingestion of placebo, methionine (0.1 mg/kg), vitamin C (2 g) and methionine plus vitamin C. Blood flow and platelet aggregation responses were unaffected by methionine loading. Substance P caused dose-dependent increases in plasma tissue plasminogen activator (t-PA) antigen (from 3.0+/-0.1 to 4.7+/-0.4 ng/ml; P<0.001) and activity (from 1.2+/-0.2 to 4.2+/-0.4 i.u./ml; P<0.001), which were augmented during acute methionine loading (4.7+/-0.4 to 5.6+/-0.5 ng/ml and 4.2+/-0.4 to 5.5+/-0.9 i.u./ml respectively; P</=0.05). Moreover, the estimated net release of t-PA was enhanced during methionine loading (two-way ANOVA; P=0.02), but this was unaffected by vitamin C supplementation. We conclude that, in the absence of alterations in endothelium-dependent vasomotion or platelet aggregation, substance P-induced t-PA release is enhanced following methionine loading. This suggests that the acute endogenous fibrinolytic capacity is augmented during acute hyperhomocysteinaemia in healthy humans via an oxidation-independent mechanism.
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PMID:Effects of acute methionine loading and vitamin C on endogenous fibrinolysis, endothelium-dependent vasomotion and platelet aggregation. 1117 Dec 80

In order to describe potential hypofibrinolytic tendencies in young (< 35 years) polycystic ovary syndrome (PCOS) patients, we studied plasminogen activator inhibitor (PAI-1) system components in women without laboratory evidence of hyperinsulinism or hyperandrogenism. The study was a prospective, observational comparison and took place in a major urban infertility referral center. Age, body mass index, ovulatory status, selected androgen levels, fasting insulin and plasma lipids were measured in subjects with PCOS (n = 39) and normal control subjects (n = 20). Women with PCOS had higher mean serum total testosterone and androstenedione levels compared with controls (56.4 versus 40.3 ng/dl, p = 0.03, and 179 versus 133 microg/ml, p = 0.03, respectively). Mean fasting insulin levels were higher among PCOS women (p < 0.01) and were strongly correlated with PAI-1 antigen (Ag) (r = 0.46), PAI-1 activity (r = 0.43), and tissue plasminogen activator (t-PA) (r = 0.5). Correlations were evident in both PCOS and control subjects. Mean PAI-1 Ag, PAI-1 activity, and t-PA levels were significantly elevated (p = 0.003, 0.001, and 0.001, respectively) in PCOS. ANOVA was performed to control for insulin effect; a trend toward elevated PAI-1 in PCOS persisted but was no longer statistically significant (p = 0.24). PAI-1 activity elevation remained in PCOS women with mean fasting insulin levels < 10 mIU/ml (p = 0.02), yet the difference became less significant when insulin was controlled (p = 0.38). Although these data confirm known associations between insulin and PAI-1 derangements, this is the first study to quantify discrete PAI-1 elevations that persist in the setting of PCOS even with normal or low ambient insulin levels. Additional prospective studies are needed to determine whether this altered PAI-1 state is associated with a clinically important hypofibrinolytic condition and subsequent poor reproductive outcome.
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PMID:Absence of profound hyperinsulinism in polycystic ovary syndrome is associated with subtle elevations in the plasminogen activator inhibitor system. 1285 31

There is a common belief in a class effect among angiotensin-converting enzyme (ACE) inhibitors. This is unsubstantiated for acute myocardial infarction (AMI). Because vascular tissue is a source of the endogenous fibrinolytic markers, and ACE inhibition in vascular tissue favorably influences the fibrinolytic system, the authors hypothesized that a high-tissue-penetrating ACE inhibitor would provide a more favorable reduction in plasminogen activator inhibitor-1 (PAI-1) and an increase in tissue plasminogen activator (t-PA) after AMI compared to a low-tissue-penetrating ACE inhibitor. In a randomized open-label trial, patients received the high-tissue-penetrating quinapril (n = 15) or low-tissue-penetrating enalapril (n = 15) immediately following an AMI. PAI-1 and t-PA antigen (ng/mL) were measured at baseline and through 14 days of treatment. There was no difference in baseline PAI-1 or t-PA antigen between treatments. PAI-1 antigen trended toward being lower with quinapril versus enalapril on day 1 (24.44 +/- 14.96 vs. 36.94 +/- 19.49, respectively, p = 0.059) and was significantly lower on day 3 (17.32 +/- 9.57 vs. 27.49 +/- 9.61, respectively, p = 0.009). Analysis of PAI-1 antigen over time by two-factor ANOVA with replication found significantly lower concentrations of PAI-1 antigen over the entire treatment period with quinapril versus enalapril (p < 0.003). This investigation of ACE inhibitor tissue-penetrating influence on markers of reinfarction risk suggests there may be a greater early reduction in PAI-1 with a more highly tissue-penetrating ACE inhibitor.
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PMID:Questioning a class effect: does ACE inhibitor tissue penetration influence the degree of fibrinolytic balance alteration following an acute myocardial infarction? 1474 23

Blood flow and plasma fibrinolytic factors were measured on five occasions in both forearms of eight otherwise healthy male smokers during unilateral brachial artery infusion of the endothelium-dependent vasodilator, substance P (2 to 8 pmol/min), and the endothelium-independent vasodilator, sodium nitroprusside (2 to 8 microg/min). On the first occasion, intra-arterial vitamin C was co-infused at 25 mg/min. On subsequent occasions, subjects attended after 28 and 35 days treatment with oral vitamin C (1 g daily) or placebo in a double-blind randomized crossover design still smoking but with and without acute smoke inhalation (3 cigarettes over 30 minutes). Basal plasma ascorbate concentrations increased from 37 +/- 6 micromol/L to 105 +/- 11 micromol/L following oral vitamin C supplementation (P = 0.002). Substance P caused dose-dependent increases in forearm blood flow (P < 0.001, ANOVA) and t-PA release (P < 0.05, ANOVA) that was unaffected by acute recent smoke inhalation, intra-arterial vitamin C, or oral vitamin C administration (p = ns). Likewise there were no effects on sodium nitroprusside-induced vasodilatation (p = ns). Neither acute local intra-arterial nor prolonged oral vitamin C supplementation reverses smoking-related endothelial dysfunction and impaired endogenous t-PA release. We conclude that the adverse vascular actions of smoking are not principally mediated through oxidative stress.
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PMID:Vitamin C has no effect on endothelium-dependent vasomotion and acute endogenous fibrinolysis in healthy smokers. 1517 66

We have shown that the capacity for local release of tissue-type plasminogen activator (tPA) from the vascular endothelium is impaired in patients with primary hypertension. Because this response is an important protective mechanism against intravascular clotting, we investigated whether this system is also defective in patients with advanced chronic kidney disease and hypertension. Nine nondiabetic nonsmoking men with chronic kidney disease (glomerular filtration rate 11 to 28 mL/min x 1.73 m2; aged 33 to 75 years) were compared with age-matched healthy controls. Intraarterial infusions of desmopressin, methacholine, and sodium nitroprusside were given locally in the brachial artery. Forearm blood flow was measured by venous occlusion plethysmography and blood collected repeatedly during the desmopressin infusion for determination of stimulated net and total cumulated release of tPA. The maximal release rate of active tPA (P<0.05) and the capacity for acute tPA release were markedly impaired in the renal patients as compared with healthy subjects (ANOVA, P=0.013). Accordingly, the accumulated release of tPA was 1905 (SEM 366) and 3387 (718) ng/L tissue, respectively (P<0.05). However, there were no significant differences in vasodilator responses between the groups. Thus, patients with advanced chronic kidney disease and hypertension have a markedly impaired capacity for acute release of tissue plasminogen activator, despite preserved endothelium-dependent vasodilation. This defect may contribute to a defective local defense against arterial thrombosis.
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PMID:Impaired endothelial release of tissue-type plasminogen activator in patients with chronic kidney disease and hypertension. 1524 48

Angiotensin II stimulates the expression of tissue factor (TF) and plasminogen activator inhibitor type-1 (PAI-1), and AT1 receptor blockade (ARB) reduces PAI-1 and TF activities in experimental studies. We investigated the effects of ARBs on TF activity, tissue plasminogen activator (tPA), PAI-1 antigen levels, plasma renin activity (PRA) and aldosterone levels in hypertensive patients. Placebo, losartan 100mg, irbesartan 300 mg, and candesartan 16 mg daily were administered to 122 patients for 2 months. Compared with placebo, ARBs significantly reduced TF activity (P <0.001 by ANOVA), and candesartan was the most potent. Compared with placebo or losartan, irbesartan and candesartan significantly lowered plasma levels of PAI-1 antigen (P <0.001 by ANOVA) with no differences between the two. Compared with placebo, all ARBs lowered plasma levels of aldosterone (P=0.012 by ANOVA) and increased PRA (P=0.005 by ANOVA). There were significant correlations between the degree of change in TF activity and PAI-1 antigen levels (r=0.458, P <0.0001) and between the change in TF activity and PRA (r=-0.296, P=0.006), but not with the magnitude of reduction in blood pressure following ARB therapy. ARBs significantly reduced TF activity, PAI-1 antigen levels, and aldosterone levels in hypertensive patients. The clinical significance of the varying potency of some ARBs needs to be further investigated.
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PMID:Angiotensin II type 1 receptor blockers reduce tissue factor activity and plasminogen activator inhibitor type-1 antigen in hypertensive patients: a randomized, double-blind, placebo-controlled study. 1548 78

Thrombus formation within hemodialysis catheters contributes to inadequate dialysis and adverse patient outcomes. A thrombolytic agent may be required to restore patency and improve blood flow. This study evaluates the efficacy of instilling low dose (1 mg/ml) t-PA in catheter lumens to restore patency in malfunctioning catheters. t-PA was utilized to treat suspected catheter thrombus over a four-month period. Seventeen patients with 21 catheters (12 temporary, 9 permanent) received 40 doses of t-PA. Catheter function was restored in 39 of 40 cases (97.5%). Significant improvement in blood flow was confirmed by paired t-test (p < 0.001). Sustained improvement in blood flow was confirmed by ANOVA (p < 0.001). The mean primary patency of all catheters was 29.7 days (SD = 27.0 days). No adverse patient effects were noted. These results demonstrate that t-PA can safely and effectively restore blood flow and extend patency in hemodialysis catheters.
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PMID:Tissue plasminogen activator (t-PA) efficacy in the restoration of hemodialysis catheter function. 1571 85

The increased risk for myocardial infarction and ischemic stroke in primary hypertension suggests that the condition is associated with prothrombotic mechanisms. We have shown that patients with hypertension have an impaired capacity for acute endothelial tissue-type plasminogen activator (t-PA) release, an important local protective response to prevent formation of intravascular thrombi. The aim of the present study was to investigate whether this impairment could be restored by the lowering of blood pressure. The capacity for acute t-PA release in response to intraarterial infusion of substance P at 8 pmol/min was investigated in a perfused-forearm study in 20 hypertensive patients (12 men and 8 women). Studies were performed when patients were untreated and after 8 weeks of randomized treatment with lisinopril or felodipine that lowered blood pressure by 26/10 and 24/12 mm Hg, respectively. The t-PA release response increased significantly with treatment (ANOVA, P=0.0001), with a similar effect in the 2 treatment groups. The peak release of t-PA increased from 257 (58) to 445 (77) ng/min x L/tissue(-1) (t test, P=0.02). Also, treatment shortened the average time to peak secretion from 6.7 (1.4) to 2.7 (0.3) min (t test, P=0.01). In 6 patients with a delayed secretory peak (9 minutes or later), treatment normalized the response (chi2 test, P=0.008). Antihypertensive therapy restores the capacity for acute t-PA release and improves the rapidity of the response in patients with primary hypertension. Similar responses with the 2 regimens suggest that the improvement is related to the blood pressure reduction as such. This effect may contribute to the thromboprotective effect of antihypertensive treatment.
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PMID:Impaired capacity for stimulated fibrinolysis in primary hypertension is restored by antihypertensive therapy. 1652 Apr 4

We hypothesized that restenosis after coronary stenting is predicted by elevated levels of markers of thrombus formation and inflammation. Plasma levels of representative markers of inflammation, the thrombin and plasmin activation systems and adhesion molecules were measured in 59 patients with stable angina pectoris before, immediately after and 6 hours (h), 12 h, 24 h, one month and six months after elective stent implantation (radioactive phosphorus-32 stents/RSs/ n = 16, bare-metal stents/BMSs/ n = 43). All patients underwent clinical and angiographic follow-up (FUP) six months after stenting. RSs had significantly higher angiographic severity of restenosis than BMSs (47.1 +/- 20.1% vs. 27.6 +/- 22.0%, p = 0.003). Repeated measures ANOVA revealed significant differences between the BMS and RS groups as regards the increases in plasma levels of vascular cell adhesion molecule-1 (VCAM-1, p = 0.022), plasminogen activator inhibitor-1 (PAI-1, p = 0.047), tissue-type plasminogen activator (tPA, p = 0.047) and CD40 ligand (CD40L, p = 0.038). tPA levels tended to increase immediately after stenting in both groups, whereas the PAI-1 level one month after stenting was elevated significantly only in the RS group. In the RS group, the plasma levels of CD40L were increased at 24 h and six months after stenting, and the VCAM-1 level rose immediately after stenting and remained high during the FUP. Multivariate analysis on pooled laboratory data of both groups revealed elevated levels of VCAM-1 at 12 h and at six months as significant predictors of the severity of stent restenosis. In conclusion, the process of inflammation and thrombosis occurring after coronary interventions seems to be prolonged and enhanced in patients with high-grade restenosis at the follow up.
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PMID:Time course of prothrombotic and proinflammatory substance release after intracoronary stent implantation. 1839 32


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