Migraine-Associated Common Genetic Variants Confer Greater Risk of Posterior vs. Anterior Circulation Ischemic Stroke☆.

OBJECTIVE: To examine potential genetic relationships between migraine and the two distinct phenotypes posterior circulation ischemic stroke (PCiS) and anterior circulation ischemic stroke (ACiS), we generated migraine polygenic risk scores (PRSs) and compared these between PCiS and ACiS, and separately vs. non-stroke control subjects. METHODS: Acute ischemic stroke cases were classified as PCiS or ACiS based on lesion location on diffusion-weighted MRI. Exclusion criteria were lesions in both vascular territories or uncertain territory; supratentorial PCiS with ipsilateral fetal posterior cerebral artery; and cases with atrial fibrillation. We generated migraine PRS for three migraine phenotypes (any migraine; migraine without aura; migraine with aura) using publicly available GWAS data and compared mean PRSs separately for PCiS and ACiS vs. non-stroke control subjects, and between each stroke phenotype. RESULTS: Our primary analyses included 464 PCiS and 1079 ACiS patients with genetic European ancestry. Compared to non-stroke control subjects (n=15396), PRSs of any migraine were associated with increased risk of PCiS (p=0.01-0.03) and decreased risk of ACiS (p=0.010-0.039). Migraine without aura PRSs were significantly associated with PCiS (p=0.008-0.028), but not with ACiS. When comparing PCiS vs. ACiS directly, migraine PRSs were higher in PCiS vs. ACiS for any migraine (p=0.001-0.010) and migraine without aura (p=0.032-0.048). Migraine with aura PRS did not show a differential association in our analyses. CONCLUSIONS: Our results suggest a stronger genetic overlap between unspecified migraine and migraine without aura with PCiS compared to ACiS. Possible shared mechanisms include dysregulation of cerebral vessel endothelial function.

Technological readiness and implementation of genomic-driven precision medicine for complex diseases.

The fields of human genetics and genomics have generated considerable knowledge about the mechanistic basis of many diseases. Genomic approaches to diagnosis, prognostication, prevention and treatment - genomic-driven precision medicine (GDPM) - may help optimize medical practice. Here, we provide a comprehensive review of GDPM of complex diseases across major medical specialties. We focus on technological readiness: how rapidly a test can be implemented into health care. Although these areas of medicine are diverse, key similarities exist across almost all areas. Many medical areas have, within their standards of care, at least one GDPM test for a genetic variant of strong effect that aids the identification/diagnosis of a more homogeneous subset within a larger disease group or identifies a subset with different therapeutic requirements. However, for almost all complex diseases, the majority of patients do not carry established single-gene mutations with large effects. Thus, research is underway that seeks to determine the polygenic basis of many complex diseases. Nevertheless, most complex diseases are caused by the interplay of genetic, behavioural and environmental risk factors, which will likely necessitate models for prediction and diagnosis that incorporate genetic and non-genetic data.

Neglect and aphasia in the acute phase as predictors of functional outcome 7 years after ischemic stroke.

BACKGROUND AND PURPOSE: Visuospatial inattention (VSI) and language impairment (LI) are often present early after stroke and associations with an unfavorable short-term functional outcome have been reported. The purpose of this study was to investigate whether a screening of VSI and LI as indicators of cortical symptoms early after stroke could predict long-term functional outcomes. METHODS: A consecutive cohort of 375 patients with ischemic stroke was assessed for the occurrence of VSI at a median of 7 days after admission (interquartile range, 1-5 days) using the Star Cancellation Test and for LI (within the first 7 days) with the language item in the Scandinavian Stroke Scale. Seven years later, functional outcomes were assessed by the modified Rankin scale and Frenchay Activities Index in 235 survivors without recurrent stroke. Relationships between baseline predictors and functional outcome at 7 years were analyzed with bivariate correlations and multiple categorical regressions with optimal scaling. RESULTS: The regression model significantly explained variance in the modified Rankin scale (R2 = 0.435, P < 0.001) and identified VSI (P = 0.001) and neurological deficits (P < 0.001; Scandinavian Stroke Scale score without the language item) as the significant independent predictors. The model for Frenchay Activities Index was also significant (R2 = 0.269, P < 0.001) with VSI (P = 0.035) and neurological deficits (P < 0.001) as significant independent predictors. CONCLUSIONS: Visuospatial inattention at acute stroke has an independent impact on long-term functional outcomes. Early recognition may enable targeted rehabilitative interventions.

Exome array analysis of ischaemic stroke: results from a southern Swedish study.

BACKGROUND AND PURPOSE: Genome-wide association (GWA) studies have identified a few risk loci for ischaemic stroke, but these variants explain only a small part of the genetic contribution to the disease. Coding variants associated with amino acid substitutions or premature termination of protein synthesis could have a large effect on disease risk. We performed an exome array analysis for ischaemic stroke. METHODS: Patients with ischaemic stroke (n = 2385) and control subjects (n = 6077) from three Swedish studies were genotyped with the Illumina HumanOmniExpressExome BeadChip. Single-variant association analysis and gene-based tests were performed of exome variants with minor allele frequency of < 5%. A separate GWA analysis was also performed, based on 700 000 genotyped common markers and subsequent imputation. RESULTS: No exome variant or gene was significantly associated with all ischaemic stroke after Bonferroni correction (all P > 1.8 × 10-6 for single-variant and >4.15 × 10-6 for gene-based analysis). The strongest association in single-variant analysis was found for a missense variant in the DNAH11 gene (rs143362381; P = 5.01 × 10-6 ). In gene-based tests, the strongest association was for the ZBTB20 gene (P = 7.9 × 10-5 ). The GWA analysis showed that the sample was homogenous (median genomic inflation factor = 1.006). No genome-wide significant association with overall ischaemic stroke risk was found. However, previously reported associations for the PITX2 and ZFHX3 gene loci with cardioembolic stroke subtype were replicated (P = 7 × 10-15 and 6 × 10-3 ). CONCLUSIONS: This exome array analysis did not identify any single variants or genes reaching the pre-defined significance level for association with ischaemic stroke. Further studies on exome variants should be performed in even larger, well-defined and subtyped samples.

Are 25 SNPs from the CARDIoGRAM study associated with ischaemic stroke?

BACKGROUND AND PURPOSE: The Coronary Artery Disease Genome-Wide Replication and Meta-Analysis Study (CARDIoGRAM) reported 25 single-nucleotide polymorphisms (SNPs) on 15 chromosomes to be associated with coronary artery disease (CAD) risk. Because common vascular risk factors are shared between CAD and ischaemic stroke (IS), these SNPs may also be related to IS overall or one or more of its pathogenetic subtypes. METHODS: We performed a candidate gene study comprising 3986 patients with IS and 2459 control subjects. The 25 CAD-associated SNPs reported by CARDIoGRAM were examined by allelic association analysis including logistic regression. Weighted and unweighted genetic risk scores (GRSs) were also compiled and likewise analysed against IS. We furthermore considered the IS main subtypes large-vessel disease (LVD), small-vessel disease and cardioembolic stroke [according to Trial of Org 10172 in Acute Stroke Treatment (TOAST)] separately. RESULTS: SNP rs4977574 on chromosome 9p21.3 was associated with overall IS [odds ratio (OR) = 1.12; 95% confidence interval (CI): 1.04-1.20; P = 0.002] as well as LVD (OR = 1.36; 95% CI: 1.13-1.64; P = 0.001). No other SNP was significantly associated with IS or any of its main subtypes. Analogously, the GRSs did not show any noticeable effect. CONCLUSIONS: Besides the previously reported association with SNPs on chromosome 9p21, this study did not detect any significant association between IS and CAD-susceptible genetic variants. Also, GRSs compiled from these variants did not predict IS or any pathogenetic IS subtype, despite a total sample size of 6445 participants.

The prediction of functional dependency by lateralized and non-lateralized neglect in a large prospective stroke sample.

BACKGROUND AND PURPOSE: Lateralized and non-lateralized impairments in visual attention have been identified as important components in patients with visuospatial neglect. This study investigated the course of these two phenomena across time in relation to neurological symptoms and functional outcome in a large consecutive and prospective stroke sample. METHODS: A total of 375 consecutive stroke patients were divided into three groups (lateralized, non-lateralized or no visual inattention) acutely and 3 months post-stroke using the star cancellation test. Neurological impairments, localization of brain damage, asymmetry in clinical symptoms and functional outcome were assessed. Possible group differences were analysed, and stepwise logistic regressions were performed to examine the relative importance of predictors of functional dependency. RESULTS: Participants with acute lateralized inattention differed (P ≤ 0.05) from the other two groups by more often exhibiting severe neurological symptoms, functional dependency and persisting visual inattention. The regression analyses selected acute lateralized inattention as an important and independent predictor of functional dependency following right hemisphere damage, but not following left hemisphere damage. CONCLUSIONS: The results emphasize the prognostic value of lateralized inattention and the importance of separating lateralized and non-lateralized symptoms of visual inattention at the commencement of rehabilitation.

Stroke subtype predicts outcome in young and middle-aged stroke sufferers.

OBJECTIVES: There are few studies on long-term outcome after ischemic stroke (IS) for young and middle-aged stroke sufferers in relation to etiologic subtypes. Here, we report 2-year outcome in the Sahlgrenska Academy Study on Ischemic Stroke (SAHLSIS). MATERIALS AND METHODS: SAHLSIS comprises 600 patients with IS before the age of 70 years. Etiologic subtype of IS was classified according to Trial of Org 10172 in Acute Stroke Treatment (TOAST). Recurrent vascular events and death were registered using several overlapping methods. Functional outcome was assessed according to the modified Rankin Scale (mRS). RESULTS: After 2 years, 55 (9.2%) patients had suffered a recurrent stroke, 15 (2.5%) had a transient ischemic attack (TIA), 4 (0.7%) had a coronary event, and 24 (4.0%) had died. The number of recurrent stroke, TIA, and death differed significantly between etiologic stroke subtypes. The highest rates were observed in large-vessel disease (LVD), whereas small-vessel disease and cryptogenic stroke showed the lowest recurrence and mortality rates. LVD was a significant predictor of the composite outcome (recurrent stroke, TIA, coronary event and/or death) independently of cardiovascular risk factors and stroke severity. Stroke subtype also predicted functional outcome 2 years after index stroke, but this association was not retained after adjustment for stroke severity. CONCLUSIONS: In young and middle-aged stroke patients, stroke subtype predicts recurrent vascular events and/or death 2 years after index stroke independently of cardiovascular risk factors and stroke severity. Thus, it is important to take the etiologic subtype of IS in account when assessing the risk of recurrence both in the clinical setting and in future studies.

Genetic variation on chromosome 9p21 shows association with the ischaemic stroke subtype large-vessel disease in a Swedish sample aged ≤ 70.

BACKGROUND: The aim of this study was to investigate whether we could replicate a recent finding of an association between genetic variants on chromosome 9p21 and the ischaemic stroke (IS) subtype large-vessel disease (LVD). METHODS: The Sahlgrenska Academy Study on Ischemic Stroke comprises 844 patients with IS, who suffered IS before reaching the age of 70, and 668 healthy controls. IS subtype was defined according to the TOAST criteria, and 111 patients were categorized as LVD. Seven single-nucleotide polymorphisms (SNPs) on 9p21 were analyzed. Functional outcome was assessed 3 months after IS using the modified Rankin scale. RESULTS: The SNP rs7857345 showed a significant association with the subtype LVD independent of traditional vascular risk factors. In addition, an association between rs7857345 and functional outcome after LVD was observed. CONCLUSION: In this relatively young sample of patients with IS, genetic variation on 9p21 is associated with LVD.

Genetic variation in complement component C3 shows association with ischaemic stroke.

BACKGROUND AND PURPOSE: The aim of this study was to investigate whether genetic variation at the third complement component (C3) locus is associated with ischaemic stroke (IS). METHODS: The Sahlgrenska Academy Study on Ischaemic Stroke comprises 844 patients with IS, and 668 healthy controls. Sixteen SNPs were analyzed. RESULTS: Two SNPs, rs2277984 and rs3745565, showed a significant association with overall IS. The SNP rs2277984 also showed association with the IS subtype cryptogenic stroke. These associations were independent of hypertension, diabetes, and smoking. The independent association between rs3745565 and overall IS withstands correction for multiple testing. CONCLUSION: In this sample of patients with IS, genetic variation in C3 is associated with IS.

Detailed phenotyping of posterior vs. anterior circulation ischemic stroke: a multi-center MRI study.

OBJECTIVE: Posterior circulation ischemic stroke (PCiS) constitutes 20-30% of ischemic stroke cases. Detailed information about differences between PCiS and anterior circulation ischemic stroke (ACiS) remains scarce. Such information might guide clinical decision making and prevention strategies. We studied risk factors and ischemic stroke subtypes in PCiS vs. ACiS and lesion location on magnetic resonance imaging (MRI) in PCiS. METHODS: Out of 3,301 MRIs from 12 sites in the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Genetics Network (SiGN), we included 2,381 cases with acute DWI lesions. The definition of ACiS or PCiS was based on lesion location. We compared the groups using Chi-squared and logistic regression. RESULTS: PCiS occurred in 718 (30%) patients and ACiS in 1663 (70%). Diabetes and male sex were more common in PCiS vs. ACiS (diabetes 27% vs. 23%, p < 0.05; male sex 68% vs. 58%, p < 0.001). Both were independently associated with PCiS (diabetes, OR = 1.29; 95% CI 1.04-1.61; male sex, OR = 1.46; 95% CI 1.21-1.78). ACiS more commonly had large artery atherosclerosis (25% vs. 20%, p < 0.01) and cardioembolic mechanisms (17% vs. 11%, p < 0.001) compared to PCiS. Small artery occlusion was more common in PCiS vs. ACiS (20% vs. 14%, p < 0.001). Small artery occlusion accounted for 47% of solitary brainstem infarctions. CONCLUSION: Ischemic stroke subtypes differ between the two phenotypes. Diabetes and male sex have a stronger association with PCiS than ACiS. Definitive MRI-based PCiS diagnosis aids etiological investigation and contributes additional insights into specific risk factors and mechanisms of injury in PCiS.

Impaired myocardial t-PA release in patients with coronary artery disease.

AIMS: Myocardial ischemia remains a significant perioperative complication in coronary artery disease (CAD) patients. We hypothesized that noxious stimuli during major surgery are associated with an acute release of tissue-type plasminogen activator (t-PA) into the coronary circulation, and that this response is reduced by CAD. METHODS AND RESULTS: Two patient groups, with (n=14) and without (n=8) CAD, were studied during the initial phase of heart surgery. After retrograde great cardiac vein catheterizations during closed-chest conditions, coronary arterial-venous concentration gradients of t-PA and plasminogen activator inhibitor type-1 (PAI-1) were measured together with coronary blood flow measurements, allowing derivation of coronary net release rates. Pre-surgery atrial pacing, performed to evaluate the influence of increases in heart rate (+ 40 beats/min) and coronary blood flow (+ 80 ml/min), did not significantly alter coronary net release of t-PA or PAI-1 in either patient group. Sternotomy induced a prominent increase in coronary net release of both total and active t-PA in the non-CAD group. This response was considerably reduced in the CAD group. CONCLUSIONS: This study provides the first analysis of coronary t-PA release during major surgery and demonstrates a deficient local endothelial t-PA release in patients with CAD. This suggests a reduced local fibrinolytic capacity in CAD patients, which may explain the increased risk for coronary thrombosis in this patient group.

Time- and dose-related regional fluxes of tissue-type plasminogen activator in anesthetized endotoxemic pigs.

BACKGROUND: Acute endotoxinemia elicits an early fibrinolytic response. This study analyzes the effects of the dose and duration of endotoxin infusion on arterial levels of tissue-type plasminogen activator (tPA) and pulmonary, mesenteric and hepatic plasma tPA fluxes. METHODS: Pigs were randomized to receive an acute, high-dose (for 6 h, n=13, high ETX) or a prolonged, low-dose (for 18 h, n=18, low ETX) infusion of endotoxin or saline vehicle alone (for 18 h, n=14, control). All animals were fluid resuscitated to maintain a normodynamic circulation. Systemic and regional blood flows were measured and arterial, pulmonary arterial, portal and hepatic venous blood samples were analyzed to calculate regional net fluxes of tPA. Plasma tumor necrosis factor (TNF-alpha) levels were analyzed. RESULTS: Mesenteric tPA release and hepatic uptake increased maximally at 1.5 h in ETX groups related to dose. Maximal mesenteric tPA release [high ETX 612 (138-1185) microg/min/kg, low ETX 72 (32-94) microg/min/kg, median+/-interquartile range] and hepatic tPA uptake [high ETX -1549 (-1134 to -2194) microg/min/kg, low ETX -153 (-105 to -307) microg/min/kg] correlated to TNF-alpha levels. Regional tPA fluxes returned to baseline levels at 6 h in both ETX groups and also remained low during sustained low ETX. No changes were observed in control animals. CONCLUSIONS: Endotoxemia induces an early increase in mesenteric tPA release and hepatic tPA uptake related to the severity of endotoxemia. The time patterns of changes in mesenteric and hepatic tPA fluxes are similar in acute high-dose endotoxemia and sustained low-dose endotoxemia.

Genome-wide analysis of genetic determinants of circulating factor VII-activating protease (FSAP) activity.

Essentials Knowledge of genetic regulators of plasma factor VII activating protease (FSAP) levels is limited. We performed a genome-wide analysis of variants influencing FSAP activity in Scandinavian cohorts. We replicated an association for Marburg-1 and identified an association for a HABP2 stop variant. We identified a novel locus near ADCY2 as a potential additional regulator of FSAP activity. SUMMARY: Background Factor VII-activating protease (FSAP) has roles in both coagulation and fibrinolysis. Recent data indicate its involvement in several other processes, such as vascular remodeling and inflammation. Plasma FSAP activity is highly variable among healthy individuals and, apart from the low-frequency missense variant Marburg-I (rs7080536) in the FSAP-encoding gene HABP2, determinants of this variation are unclear. Objectives To identify novel genetic variants within and outside of the HABP2 locus that influence circulating FSAP activity. Patients/Methods We performed an exploratory genome-wide association study (GWAS) on plasma FSAP activity amongst 3230 Swedish subjects. Directly genotyped rare variants were also analyzed with gene-based tests. Using GWAS, we confirmed the strong association between the Marburg-I variant and FSAP activity. HABP2 was also significant in the gene-based analysis, and remained significant after exclusion of Marburg-I carriers. This was attributable to a rare HABP2 stop variant (rs41292628). Carriers of this stop variant showed a similar reduction in FSAP activity as Marburg-I carriers, and this finding was replicated. A secondary genome-wide significant locus was identified at a 5p15 locus (rs35510613), and this finding requires future replication. This common variant is located upstream of ADCY2, which encodes a protein catalyzing the formation of cAMP. Results and Conclusions This study verified the Marburg-I variant to be a strong regulator of FSAP activity, and identified an HABP2 stop variant with a similar impact on FSAP activity. A novel locus near ADCY2 was identified as a potential additional regulator of FSAP activity.

Infusion of epinephrine augments pressor responses to mental stress.

Circulating epinephrine may facilitate neural release of norepinephrine both during and after periods of sympathoadrenal activation by stimulation of prejunctional beta-adrenergic receptors. The present study was undertaken to examine possible effects and aftereffects of epinephrine on the hemodynamic reactivity to mental stress. To this end, two strictly standardized mental stress tests were performed in 14 normotensive men during and 1 hour after double-blind infusion of epinephrine (50 ng x kg-1 x min-1) or placebo given in random order. During epinephrine infusion, the systolic pressor response to psychosocial stress was augmented (+17 versus +10 mm Hg during epinephrine and placebo, respectively; p = 0.02). This was associated with an attenuated post-stress recovery, with the result that the stress exposure induced a prolonged elevation of systolic blood pressure. Heart rate was elevated and diastolic blood pressure lowered during epinephrine infusion without any change in the reactivity to stress. One hour after the end of the epinephrine infusion resting heart rate was still maintained on a higher level independently of level of arousal, but heart rate and blood pressure responses to stress were unaffected. The findings are consistent with the hypothesis that high circulating epinephrine levels amplify pressor responses to mental stress but do not support the suggestion that short-term infusion of epinephrine causes prolonged augmentation of blood pressure responses to psychosocial stress.

Enhanced levels of tissue-type plasminogen activator in borderline hypertension.

Despite effective antihypertensive therapy, essential hypertension is still associated with considerable residual risk of cardiovascular complications. The aim of the present study was to investigate the state of the endogenous fibrinolytic system in young subjects with borderline hypertension. Thirty-nine young (age, 24 to 34 years) male subjects with borderline hypertension (systolic BP [SBP] 140 to 160 mm Hg and/or diastolic BP [DBP] 85 to 95 mm Hg) and 17 normotensive control subjects (age, 22 to 31 years; SBP 110 to 130 and DBP 60 to 80 mm Hg) were recruited from a population screening. Plasma levels of tissue-type plasminogen activator (t-PA) antigen and activity and plasminogen activator inhibitor 1 (PAI-1) antigen were determined at rest and in response to a venous occlusion test. Borderline-hypertensive subjects had metabolic and anthropometric characteristics similar to normotensive individuals. In comparison with normotensive subjects, borderline-hypertensive subjects had higher plasma concentration of t-PA antigen both at rest and after venous occlusion but similar levels of t-PA activity or PAI-1 antigen. The increase in t-PA antigen and activity in response to venous occlusion was significantly greater in borderline-hypertensive subjects than in normotensive control subjects (P < .0001 and P = .003, respectively). In stepwise regression analyses, 24-hour mean arterial pressure emerged as the single most powerful predictor of t-PA antigen levels, but body mass index was the most important determinant of t-PA activity and PAI-1 antigen. However, PAI-1 was explained by both body mass index (partial r = .48, P < .001) and 24-hour mean arterial pressure (partial r = .29, P < .05). Thus, early hypertension may be associated with significant alterations in endogenous fibrinolysis.

Genetic variation at the human tissue-type plasminogen activator (tPA) locus: haplotypes and analysis of association to plasma levels of tPA.

Tissue-type plasminogen activator (tPA) plays a key role in thrombus dissolution and plasma levels of tPA have been associated with cardiovascular disease. We have previously resequenced regulatory and coding regions of the human tPA gene (PLAT) and identified eight single-nucleotide polymorphisms (SNPs). In a small experimental study, four common variants were associated with invasively determined vascular tPA release rates. The aim of the present study was to investigate whether there is an association between genetic variants at this locus and plasma levels of tPA. To this end, 240 Swedish individuals without cardiovascular disease were typed for the eight SNPs and an Alu insertion polymorphism at the PLAT locus, as well as for a polymorphism in the plasminogen activator inhibitor type 1 (PAI-1) promoter (PAI-1 -675 4G>5G). Stepwise regression analysis, with established predictors of plasma tPA including plasma PAI-1 and genetic variants, showed that neither genotypes nor haplotypes were major contributors to plasma tPA. The results also showed that the level of linkage disequilibrium was high at the PLAT locus, as demonstrated by the fact that only three haplotypes had a frequency above 5%. In conclusion, in the present study neither genetic variation at the PLAT locus nor the PAI-1 -675 4G>5G polymorphism was strong predictors of plasma tPA levels, which suggests that variations in other genes contribute to the heritability of this phenotype. The results also show that three haplotypes at the PLAT locus accounted for nearly 90% of the chromosomes and that they could be defined by typing only two SNPs.

Regulation of local availability of active tissue-type plasminogen activator in vivo in man.

Free, biologically active tissue-type plasminogen activator (tPA) is the main initiator of intravascular fibrinolysis, but little is known about the regulation of active tPA on the organ level. The aim was to investigate if the local availability of active tPA on the organ level depends on the local release rate of tPA or the arterial input of tPA and plasminogen activator inhibitor type 1 (PAI-1). Also, we wanted to evaluate if plasma levels predict capacity for endothelial release of fibrinolytic proteins. Invasive perfused-forearm studies were performed in 96 healthy subjects. Local release rates of fibrinolytic proteins were assessed at baseline and during endothelial stimulation. Stimulation by methacholine and desmopressin induced a 6- and 12-fold increase in total tPA release rates, respectively. With increasing local release rates of tPA a gradually closer correlation emerged between the total tPA secretion and the forearm output of active tPA (from r = 0.102, ns to r = 0.85, P < 0.0001). Forearm availability of active tPA was not related to arterial input of either tPA or PAI-1. Release rates and plasma levels of tPA were not correlated. Baseline release rates of active tPA increased to noon. The major determinant for the local availability of active tPA is the capacity of the endothelium to release tPA rather than the arterial input of PAI-1 or tPA. Despite a molar excess of PAI-1, the majority of tPA released during stimulation does not undergo local inactivation. The capacity to release tPA locally cannot be predicted from its plasma concentration.

High capacity for tissue-type plasminogen activator release from vascular endothelium in vivo.

BACKGROUND: Tissue-type plasminogen activator (t-PA) is the key mediator of intravascular fibrinolysis. We showed recently that local administrations both of methacholine (MCH) and of desmopressin (1-desamino-8-D-arginine vasopressin, DDAVP) induced a massive local release of t-PA in the human forearm vasculature. OBJECTIVE: To determine whether the human vascular endothelium could respond to repeated stimulation with the same agonist, and, if so, to further evaluate the releasable endothelial pool of t-PA. METHOD: Seven young, healthy men participated. MCH and DDAVP were administered as local infusions into the brachial artery. In protocol 1 (n = 3) 2 microg/min MCH was infused for 2 (30 min with a free interval of 20 min). In protocol 2 (n = 4) 70 ng/min DDAVP was infused for 2 (20 min with an interval of 75 min). Dosages and time intervals were based on the different release profiles of the two drugs observed in previous studies. Brachial arterial and venous blood samples were obtained at baseline and throughout infusions. Net release of t-PA was calculated as the product of the arteriovenous concentration gradient and forearm plasma flow. RESULTS: Forearm blood flow was increased 3-4-fold by MCH and 2-3-fold by DDAVP infusions. During the first and second infusions of MCH, the average amounts of t-PA released were 1600 and 1000 ng/l forearm tissue, respectively. In contrast, DDAVP induced similar t-PA responses during both infusions; the average total releases of t-PA were 2300 and 2400 ng/l tissue, respectively. CONCLUSION: The results show that the vascular endothelium is responsive to repeated stimulation both with MCH and with DDAVP. The diminished t-PA response to the second MCH infusion can not be explained in terms of depletion of intracellular pools, in view of the large amount of t-PA released by a single infusion of DDAVP. The dynamic pool of t-PA available for release is very large, but further studies are required in order to quantify the releasable endothelial stores.

Cardiovascular responses to stress in young hypertensive women.

OBJECTIVE: The aim of the study was to investigate the haemodynamic effects of hormonal changes during the menstrual cycle in 11 hypertensive women aged between 29 and 38 years. DESIGN: In randomized order, the subjects were examined on days 2-7 (follicular phase) and on days 20-24 (luteal phase). All medication was withdrawn on average 5 weeks prior to the experiment. The results in the hypertensive group were compared with those of a control group consisting of 11 normotensive women aged between 21 and 46 years who had earlier taken part in an identical experiment. METHODS: A standardized mental stress test and a 24-h ambulatory blood pressure and heart rate recording were performed. RESULTS. Prestress resting heart rate was significantly higher in the hypertensive group and a significant difference was maintained throughout the entire stress experiment. Heart rate, systolic and diastolic blood pressure increased highly significantly in both groups during the exposure to mental stress, but no difference in heart rate or blood pressure reactivity between the normotensive and hypertensive groups was found in either phase. Heart rate reactivity did not differ during the two phases in the hypertensive group, in contrast to our previous findings in normotensives. During 24-h ambulatory recording both groups had slightly but significantly higher heart rate and systolic blood pressure in the luteal phase. In the hypertensives the diastolic blood pressure was also higher in this phase. Both groups had significantly higher serum oestradiol and progesterone levels in the luteal phase. CONCLUSIONS: The findings of the present study support the hypothesis that female sex hormones affect cardiovascular control in both normotensive and hypertensive women.

In vivo release of tissue-type plasminogen activator across the human forearm during mental stress.

We have previously shown that plasma levels of endothelium-derived tissue-type plasminogen activator (t-PA) increase during mental stress. The aim of the study was to investigate in vivo release in an intact human muscle vascular bed. Eleven healthy young males (22-36 yrs) were studied at rest and during 10 min of mental stress (forced arithmetic). Net release or uptake were assessed by arterio-venous (AV) concentration gradients across the forearm of t-PA antigen and t-PA activity, and plasminogen activator inhibitor antigen type 1 (PAI-1). Forearm blood flow was measured by venous occlusion plethysmography. At rest, there was a positive AV-difference of t-PA activity across the forearm indicating a net release of t-PA activity of approximately 3.7 fmol x min-1 x 100 ml-1 (Wilcoxon's signed rank test vs 0, p = 0.01). However, t-PA antigen showed a variable release pattern. On the average, there was a net release of 0.17 ng x min-1 x 100 ml-1 after 60 min of rest (Wilcoxon vs 0, p = 0.07). PAI-1 antigen showed net release at rest. In response to stress, forearm blood flow increased from 1.9 to 2.9 ml x min-1 x 100 ml-1 (ANOVA, p = 0.007), and net release of t-PA activity increased to 9.8 fmol x min-1 x 100 ml-1 (ANOVA, p = 0.01 compared with rest). Arterial and venous plasma t-PA levels also increased significantly during stress (ANOVA, p < 0.01). t-PA antigen showed a similar but less pronounced release pattern during stress.(ABSTRACT TRUNCATED AT 250 WORDS)