| 1. |
- Björkman, Jan-Arne, et al.
(författare)
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Cardiac sympathetic nerve stimulation triggers coronary t-PA release.
- 2003
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Ingår i: Arteriosclerosis, thrombosis, and vascular biology. - 1524-4636. ; 23:6, s. 1091-7
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: This study was undertaken to determine whether stimulation of sympathetic cardiac nerves induces release of the thrombolytic enzyme tissue-type plasminogen activator (t-PA) in the coronary vascular bed. METHODS AND RESULTS: Anesthetized pigs were studied in an open chest model. Bilateral vagotomy was performed, and sympathetic cardiac nerves were activated by electrical stimulation (1 and 8 Hz). To evaluate possible mediating effects of increased heart rate and enhanced local blood flow, tachycardia was induced by pacing and hyperemia by local infusion of sodium nitroprusside and clevedipine. Furthermore, to study the effects of alpha- and beta-adrenergic receptor stimulation, phenylephrine and isoprenaline were infused locally. In response to low- and high-frequency sympathetic stimulation, mean coronary net release of total t-PA increased approximately 6- and 25-fold, respectively. Active t-PA showed a similar response pattern. Neither tachycardia nor coronary hyperemia stimulated t-PA release. In contrast, beta-adrenergic stimulation by isoprenaline induced an approximately 6-fold increase in coronary t-PA release, whereas no significant change in release rates occurred in response to alpha-adrenergic stimulation by phenylephrine. CONCLUSIONS: Stimulation of cardiac sympathetic nerves induces a marked coronary release of t-PA, and part of this response may be mediated through stimulation of beta-adrenergic receptors.
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| 2. |
- Björkman, Jan-Arne, 1947
(författare)
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Endogenous t-PA release and pharmacological thrombolysis - Experimental animal studies of the coronary circulation
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abstract The physiologically most important activator of intravascular fibrinolysis is tissue-type plasminogen activator (t-PA) released from endothelial cells. In man, sympathomimetic drugs increase the systemic concentration of t-PA. It is therefore of interest to investigate whether cardiac sympathetic activation can induce a local t-PA release, which could counteract intra-coronary clot formation. Thrombolytic therapy with recombinant t-PA (rt-PA) is effective in acute myocardial infarction, but the treatment is limited by a fairly slow reperfusion rate and frequent early reocclusions. A potential mechanism behind early reocclusions might be that active thrombin is released from the thrombus during thrombolytic therapy. Thrombin has recently been shown to activate pro-carboxypeptidase U, which in its active form (CPU) down-regulates endogenous fibrinolysis. Therefore, one way of improving thrombolytic efficacy may be to combine rt-PA with a low-molecular weight direct thrombin inhibitor, which theoretically could have a pro-fibrinolytic effect, either by inhibition of fibrin-bound thrombin and/or by inhibition of CPU activation. An alternative way may be direct inhibition of CPU. In a porcine model, experimental activation of cardiac sympathetic nerves by electrical stimulation at 1 and 8 Hz induced 5- and 20-fold increase in the release of both total and active t-PA together with frequency-dependent increases in heart rate, blood pressure, and coronary blood flow. The t PA release was independent of the heart rate and coronary flow response, but local infusion of isoprenaline suggested that part of the t-PA response was mediated by stimulation of ?-adrenergic receptors. Next, we studied the combined effect of rt-PA and thrombin inhibitors (melagatran, hirudin and heparin) in a canine model of copper coil-induced coronary thrombosis. The pro-fibrinolytic effect of rt-PA, either measured as patency rate or time-to-patency, was significantly enhanced with the low-molecular weight direct thrombin inhibitor melagatran, but to a lesser degree by hirudin and heparin. In the same model it was shown that active CPU is produced locally in the coronary vascular bed during both thrombus formation and clot lysis. Inhibition of thrombin attenuated CPU formation and improved patency. A similar effect was obtained with a direct inhibitor of CPU. In conclusion, the coronary t-PA response to sympathetic stimulation may constitute a thrombo-protective defence mechanism to counteract its prothrombotic effects on the systemic level. Furthermore, direct thrombin and/or CPU inhibition may be potential targets for prevention of thrombus formation via facilitation of the endogenous fibrinolytic system.
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| 3. |
- Björkman, Jan-Arne, et al.
(författare)
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Release of tissue-type plasminogen activator (t-PA) in the splanchnic circulation of the anaesthetised pig during high sympathetic tone.
- 2010
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Ingår i: Thrombosis research. - : Elsevier BV. - 1879-2472 .- 0049-3848. ; 125:3
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: There is a substantial local release of tissue-type plasminogen activator (t-PA) in the splanchnic vascular bed, and this release is increased at high sympathetic tone. Coronary t-PA release is also significant, and this release increases during cardiac nerve stimulation and during reperfusion after 10 min of local myocardial ischemia. However, by repeated cycles of myocardial ischemia/reperfusion coronary t-PA release progressively declines. OBJECTIVES: Accordingly, we hypothesised that splanchnic t-PA release might decrease after an initial peak during maintained and long-lasting sympathetic stimulation. METHODS: In 6 anaesthetised pigs sympathetic tone was augmented by bleeding (20-25 mL/kg over 30 minutes). During the subsequent 2 hours period portal vein (draining the splanchnic vascular bed) - and arterial blood samples were drawn every 20 min and portal vein blood flow was recorded continuously in order to estimate t-PA release in the splanchnic vascular bed. RESULTS: Relatively stable haemodynamic conditions were obtained after bleeding with mean arterial blood pressure at 50 to 65 mmHg and a portal vein flow at about the 50% of baseline value. Net splanchnic t-PA release rose to a peak 40 min after bleeding, but subsequently declined towards baseline values. Arterial t-PA activity rose after the bleeding period and to a peak value at end of the observation period. CONCLUSIONS: Net splanchnic t-PA release increased only transiently during the period with increased sympathetic stimulation, whereas the arterial t-PA level remained elevated. During a strong and longlasting sympathetic stimulation the lack of a continuously augmented splanchnic t-PA release might increase the risk for intravenous splanchnic thrombosis.
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| 4. |
- Sundler Björkman, Linda, et al.
(författare)
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Increased risk of venous thromboembolism in young and middle-aged individuals with hereditary angioedema : a family study
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Ingår i: Blood. - 1528-0020.
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Tidskriftsartikel (refereegranskat)abstract
- Hereditary angioedema (HAE) due to C1 inhibitor protein (C1-INH) deficiency was recently shown to be associated with increased risk of venous thromboembolism (VTE). This is the first national family study of HAE with the aim to determine the familial risk of VTE. The Swedish Multi-Generation Register was linked to the Swedish National Patient Register during the period 1964-2018. Only HAE patients with a validated diagnosis were included in the study and were linked to their family members. Hazard ratios (HRs) and 95% confidence intervals (CIs) for VTE were calculated for HAE patients compared with relatives without HAE. Among 2,006 individuals (from 276 pedigrees of 365 patients with HAE), 103 individuals were affected by VTE. In total 35 (9.6%) of HAE patients compared to 68 (4.1%) of non-HAE relatives were affected by VTE (p<0.001). The adjusted HR for VTE among HAE patients was 2.51 (95% CI 1.67-3.77). HAE patients were younger at the first VTE than their non-HAE relatives (mean age 51 versus 63 years, p<0.001). Before the age of 70 years the HR for VTE among HAE patients was 3.62 (95%CI 2.26-5.80). The HR for VTE for HAE patients born after 1964 was 8.29 (95%CI 2.90-23.71). The HR for VTE for HAE patients born 1964 or earlier was 1.82 (95%CI 1.14-2.91). HAE is associated with VTE among young and middle-aged individuals in Swedish families with HAE. The effect size of the association is in the order of other thrombophilias. We suggest that HAE may be considered a new rare thrombophilia.
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| 5. |
- Teorell, Jan, et al.
(författare)
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Den demokratiska freden
- 2016
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Ingår i: Krig/fred: RJ:s årsbok 2016/2017. - 9789170612060 - 9789170617065
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Bokkapitel (populärvet., debatt m.m.)
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