Vessel Wall Damage Research Articles

The role of urokinase plasminogen activator and plasmin activator inhibitor-1 on vein wall remodeling in experimental deep vein thrombosis

Deep vein thrombosis (DVT) resolution instigates an inflammatory response, resulting in vessel wall damage and scarring. Urokinase-plasminogen activator (uPA) and its inhibitor, plasminogen activator inhibitor-1 (PAI-1), are integral components of the fibrinolytic system, essential for venous thrombosis (VT) resolution. This study determined the vein wall response when exposed to increased and decreased plasmin activity. A mouse inferior vena cava (IVC) ligation model in uPA -/- or PAI-1 -/- and their genetic wild types (B6/SvEv and C57/BL6, respectively) was used to create stasis thrombi, with tissue harvest at either 8 or 21 days. Tissue analysis included gene expression of vascular smooth muscle cells (alpha smooth muscle actin [αSMA], SM22) and endothelial marker (CD31), by real-time polymerase chain reaction, enzyme-linked immunosorbent assay, matrix metalloproteinase (MMP)-2 and -9 activity by zymography, and vein wall collagen by picro-Sirius red histologic analysis. A P < .05 was considered significant. Thrombi were significantly larger in both 8-day and 21-day uPA -/- as compared with wild type (WT) and were significantly smaller in both 8-day and 21-day PAI-1 -/- as compared with WT. Correspondingly, 8-day plasmin levels were reduced in half in uPA -/- and increased three-fold in PAI-1 -/- when compared with respective WT thrombi (P < .05; n = 5-6). The endothelial marker CD31 was elevated two-fold in PAI-1 -/- mice at 8 days, but reduced 2.5-fold at 21 days in uPA -/- as compared with WT (P = .02; n = 5-6), suggesting less endothelial preservation. Vein wall vascular smooth muscle cell (VSMC) gene expression showed that 8-day and 21-day PAI-1 -/- mice had 2.3- and 3.8-fold more SM22 and 1.8- and 2.3-fold more αSMA expression than respective WT (P < .05; n = 5-7), as well as 1.8-fold increased αSMA (+) cells (P ≤ .05; n = 3-5). No significant difference in MMP-2 or -9 activity was found in the PAI-1 -/- mice compared with WT, while 5.4-fold more MMP-9 was present in 21-day WT than 21-day uPA -/- (P = .03; n = 5). Lastly, collagen was ∼two-fold greater at 8 days in PAI-1 -/- IVC as compared with WT (P = .03; n = 6) with no differences observed in uPA -/- mice. In stasis DVT, plasmin activity is critical for thrombus resolution. Divergent vein wall responses occur with gain or loss of plasmin activity, and despite smaller VT, greater vein wall fibrosis was associated with lack of PAI-1.

A new nonocclusive laser-assisted coronary anastomotic connector in a rabbit model

The Excimer laser-assisted nonocclusive anastomotic technique is a nonocclusive, facilitated bypass technique that is currently Conformité Européenne and Food and Drug Administration approved for clinical application in neurosurgery. In the present study, we assessed the safety and feasibility of a newly developed Excimer laser-assisted nonocclusive anastomosis-based prototype coronary anastomotic connector in an acute rabbit abdominal aortic bypass model before application in experimental coronary bypass surgery. In addition, 2 sealants were tested to facilitate anastomotic hemostasis in the current device prototype. A total of 40 anastomoses were constructed on the abdominal aorta (3.5 mm outer diameter) of 10 rabbits. The anastomotic circumference was sealed by a surgical sealant to obtain complete hemostasis (BioGlue vs TachoSil). The anastomoses were evaluated by flow measurements construction time, hemostasis, histologic analysis, and burst pressure testing. The connector enabled a nonocclusive and fast (6.0 ± 1.7 minutes, mean ± SD [including sealing]) anastomosis construction and complete hemostasis in 95% (35/37). Sealing with BioGlue was faster than with TachoSil (19% vs 53% of construction time). Despite technical imperfections (7/40 failures to completely retrieve the flap by the laser), all 40 anastomoses were patent, showed reproducible construction with intima-adventitia apposition, streamlining thrombus coverage of the intraluminal laser rim, and no vessel wall damage. All anastomoses resisted ex vivo supraphysiologic pressures (> 300 mm Hg). The results of the present study have demonstrated that the Excimer laser-assisted nonocclusive anastomotic connector is safe and reliable and can be efficiently applied in an acute rabbit abdominal aortic bypass model. Provided the limitations can be addressed, this easy-to-use and nonocclusive technique has the potential to facilitate minimally invasive coronary bypass surgery.

Platelets have a role as immune cells

Abstract: Platelets are the primary cellular mediators of hemostasis and this function intimately acquaints them with a variety of inflammatory processes. For example, when aggregated on damaged vessel walls, activated platelets can secrete and express many pro‐ and anti‐inflammatory molecules that attract and capture circulating leukocytes and focus them on inflamed tissue. Platelets secrete several chemokines and cytokines that affect local innate immune responses by, for example, attracting neutrophils to sites of inflammation. In addition, platelets may directly regulate adaptive humoral immune responses via their expression and secretion of CD40/CD40L molecules. These studies have also suggested that platelets represent an important linkage between inflammation and thrombosis. Platelets also avidly bind to microorganisms and do so by expression of Toll‐like receptors. It appears that platelets may act as circulating sentinel cells that first encounter blood borne infectious products for presentation and activation of innate immune responses. This lecture will highlight several attributes of platelets that draw them into the realm of immunity and will discuss how platelets may be responsible for directly and indirectly controlling immune functions.

Autoimmune skin and connective tissue diseases and risk of venous thromboembolism: a population‐based case‐control study

Systemic inflammation is associated with vessel wall damage, upregulation of procoagulants, downregulation of anticoagulants, and suppression of fibrinolysis. Autoimmune diseases may therefore increase the risk of venous thromboembolism (VTE). To examine whether autoimmune skin and connective tissue diseases are associated with increased VTE risk. We conducted this population-based case-control study in northern Denmark, using administrative databases. From 1999 to 2009, we identified 14,721 VTE cases and 147,210 birth year-matched, sex-matched and county-matched population controls. The date of diagnosis/matching was considered to be the index date for cases and controls. For all study subjects, we identified hospital diagnoses of autoimmune skin or connective tissue diseases between 1977 and the index date. We used conditional logistic regression with adjustment for VTE risk factors to calculate odds ratios and 95% confidence intervals (CIs) for patients with vs. without autoimmune disease. Given the risk-set sampling design, odds ratios estimate incidence rate ratios (IRRs). Autoimmune skin disease was not associated with VTE (IRR 1.0; 95% CI 0.9-1.2). Patients with connective tissue disease had an increased VTE risk within 90 days (IRR 2.3; 95% CI 1.5-3.7) and 91-365 days (IRR 2.0; 95% CI 1.5-2.8) after diagnosis, but not thereafter (IRR 1.1; 95% CI 1.0-1.2). Among connective tissue diseases, the greatest overall risk increases were found for juvenile rheumatoid arthritis (IRR 3.0; 95% CI 1.4-6.4) and systemic lupus erythematosus (IRR 2.8; 95% CI 1.7-4.7). Autoimmune connective tissue disease was associated with an increased risk of VTE within 1 year after diagnosis, whereas skin diseases were not.

P2Y12 receptors in platelets and other hematopoietic and non-hematopoietic cells

The P2Y(12) receptor is a Gi-coupled ADP receptor first described in blood platelets where it plays a central role in the complex processes of activation and aggregation. Platelet granules store important amounts of ADP which are released upon stimulation by interaction of platelets with the damaged vessel wall. Therefore, the P2Y(12) receptor is a key player in primary hemostasis and in arterial thrombosis and is an established target of antithrombotic drugs like the thienopyridine compounds ticlopidine, clopidogrel, and prasugrel or the direct, reversible antagonists ticagrelor and cangrelor. Beyond the platelet physiology and pharmacology, recent studies have revealed the expression of the P2Y(12) receptor in other hematopoietic cells including leukocyte subtypes and microglia in the central nervous system as well as in vascular smooth muscle cells. These studies indicate putative roles of the P2Y(12) receptor in inflammatory states and diseases of the brain, lung, and blood vessels. The selective role of P2Y(12) among other P2 receptors as well as the possible impact of P2Y(12) targeting drugs in these processes remain to be evaluated.

Inflammation-Induced Thrombosis: Mechanisms, Disease Associations and Management

Although inflammation-induced thrombosis is a well-known entity, its pathogenesis remains complicated. There are complex interactions between inflammation and hemostasis, involving proinflammatory cytokines, chemokines, adhesion molecules, tissue factor expression, platelet and endothelial activation, and microparticles. Inflammation increases procoagulant factors, and also inhibits natural anticoagulant pathways and fibrinolytic activity, causing a thrombotic tendency. Besides, chronic inflammation may cause endothelial damage, resulting in the loss of physiologic anticoagulant, antiaggregant and vasodilatory properties of endothelium. However, inflammation- induced venous thrombosis may develop even in the absence of vessel wall damage. On the other hand, coagulation also augments inflammation, causing a vicious cycle. This is mainly achieved by means of thrombin-induced secretion of proinflammatory cytokines and growth factors. Platelets may also trigger inflammation by activating the dendritic cells. There are many systemic inflammatory diseases characterized by thrombotic tendency, including Behçet disease (BD), antineutrophilic cytoplasmic antibody-associated vasculitides, Takayasu arteritis, rheumatoid arthritis, systemic lupus erythematosus, antiphosholipid syndrome, familial Mediterranean fever, thromboangiitis obliterans (TAO) and inflammatory bowel diseases. Inflammation-induced thrombosis may respond to immunosuppressive (IS) treatment, as in the case of BD. However effectiveness of this treatment can not be generalized to all other inflammatory diseases. For instance, IS agents do not have any beneficial role in the management of TAO. Heparin, antiplatelet agents such as aspirin and clopidogrel, colchicine and statins also have some antiinflammatory activity. However, decreased responsiveness to aspirin and clopidogrel treatments may be observed in inflammatory diseases, due to antiplatelet resistance caused by systemic inflammation. In the present review, we aimed to discuss the details of the complex crosstalk between inflammation and hemostasis in the context of available data. We also intended to overview the major inflammatory diseases with thrombotic tendency, as well as to discuss the general principles of the management of inflammation-induced thrombosis.

NF-κB Regulates MICA Gene Transcription in Endothelial Cell through a Genetically Inhibitable Control Site

Endothelial cells form a barrier between blood and the underlying vessel wall, which characteristically demonstrates inflammatory damage in atherosclerotic disease. MICA is a highly polymorphic ligand for the activating immune receptor NKG2D and can be expressed on endothelial cells. We hypothesized that damaged vessel walls, such as those involved in atherosclerosis, might express MICA, which could contribute to the vascular immunopathology. Immune activation resulting from MICA expression could play a significant role in the development of vascular damage. We have demonstrated that TNFα up-regulates MICA on human endothelial cells. The up-regulation is mediated by NF-κB, and we have defined the regulatory control site responsible for this at -130 bp upstream of the MICA transcription start site. This site overlaps with a heat shock response element and integrates input from the two pathways. We have shown that in atherosclerotic lesions there is expression of MICA on endothelial cells. Using lentivirus-mediated gene delivery in primary human endothelial cells, we were able to inhibit the MICA response to TNFα with a truncated HSF1 that lacked a transactivation domain. This highlights the potential for transcription-based therapeutic approaches in atherosclerotic vascular disease to reduce immune-mediated endothelial and vessel wall damage.

New Insights into von Willebrand Disease and Platelet Function

Regulation of binding between von Willebrand factor (VWF) and the platelet receptor glycoprotein (GP) Ibα is one of the key steps in controlling hemostasis and thrombosis. On vascular injury at sites of high shear rates, the GPIbα interaction with subendothelial-bound VWF will initiate the tethering of circulating platelets to the vessel wall. Tethered platelets subsequently roll on the damaged vessel wall, a process that is amplified by the activation of the platelet integrin αΙΙbβ3 (GPIIb/IIIa). The initial tethering to VWF is rapidly followed by platelet binding to collagen through specific receptors (GPVI and α2β1), leading to firm adhesion, activation, and additional stable bonds mediated by αΙΙbβ3. The above described interactions can result in two distinct processes: physiological hemostasis and pathological thrombosis. Furthermore, VWF carries coagulation factor VIII, which is involved in thrombin formation that in addition to activating platelets, mediates fibrin formation and has several other actions. The importance of VWF in hemostasis is well known in patients suffering from von Willebrand disease (VWD) who present with a defect in both platelet plug and fibrin formation. Type 2B VWD is of special interest as it may provide further insight into the mechanism by which VWF promotes the adhesion of platelets to a thrombogenic surface under conditions of high shear stress. The variant phenotypic manifestations in patients affected with type 2B VWD, however, have raised the question of locus heterogeneity in VWD as a consequence of, for example, additional defects in receptor or signaling proteins mediating platelet adhesion and aggregation. Indeed, quite a few polymorphisms of platelet receptors have been associated with increased bleeding in VWD. However, many aspects of the disease remain to be elucidated. For instance, thrombin and platelet procoagulant activity may be important counterplayers to determine the severity of the bleeding complications associated with VWD.

Successful treatment of a traumatic carotid pseudoaneurysm with the Pipeline stent: Case report and review of the literature

Background:Traumatic intracranial pseudoaneurysms remain one of the most difficult vascular lesions to treat. In the case of traumatic pseudoaneurysms that may not be treated with parent vessel sacrifice, some flow diversion strategy such as stent-assistance or use of a flow diversion device is usually necessary.Case Description:In this study we describe endovascular parent vessel wall-remodeling/endoluminal reconstruction and traumatic pseudoaneurysm thrombosis through the use of the Pipeline stent and review recent reports concerning indications, safety, and efficacy for alternative pathology.Conclusion:Although currently not routinely employed in the treatment of traumatic pseudoaneurysms, the Pipeline stent may represent a safe and effective treatment alternative achieving complete endoluminal reconstruction of the damaged vessel wall.

Update on peripheral ulcerative keratitis

Ulcerative inflammation of the cornea occurs in the perilimbal cornea, and is associated with autoimmune collagen vascular and arthritic diseases. Rheumatoid arthritis is the most frequent underlying disease. The tendency for peripheral location is due to the distinct morphologic and immunologic characteristics of the limbal conjunctiva, which provides access for circulating immune complexes to the peripheral cornea via the capillary network. Deposition of immune complexes in the terminal ends of limbal vessels initiates immune-mediated vasculitis, and causes inflammatory cell and protein leakage due to vessel wall damage. Development of peripheral ulcerative keratitis associated with systemic disease may represent worsening of a potentially life-threatening disease. Accompanying scleritis, particularly the necrotizing form, is usually observed in severe cases, which may result in corneal perforation and loss of vision. Although first-line treatment with systemic corticosteroids is indicated for acute phases, immunosuppressive and cytotoxic agents are required for treatment of peripheral ulcerative keratitis associated with multisystem disorders. Recently, infliximab, a chimeric antibody against proinflammatory cytokine tumor necrosis factor-alpha, was reported to be effective in cases refractory to conventional immunomodulatory therapy. The potential side effects of these therapies require close follow-up and regular laboratory surveillance.

Comprehensive In Vitro and In Vivo Characterization of Loss and Gain-of-Function Von Willebrand Factor Collagen Binding Variants Using a Mouse Model System,

Abstract 3266Von Willebrand Factor (VWF) is a large multimeric glycoprotein that mediates platelet adhesion to the damaged blood vessel wall and subsequent platelet aggregation at the site of injury. Rare mutations in the VWF A3 domain, that disrupt collagen binding, have been found in patients with a mild bleeding phenotype. However, the analysis of these aberrant VWF-collagen interactions has been relatively limited. Thus, in this study, we have developed mouse models of collagen binding mutants and analyzed the function of the A3 and A1 domains using comprehensive in vitro and in vivo approaches. All of the collagen binding variant AAs are conserved in mice. 6 loss-of-function (S1731T, W1745C, S1783A, H1786D, A1 deletion, A3 deletion) and 1 gain-of-function (L1757A) variant was generated in the context of the mouse VWF cDNA. The 4 loss-of-function missense mutants have all been described in patients with mild bleeding phenotypes. The recombinant mouse VWFs (rmVWF) were synthesized in HEK293T cells and analyzed for type I and III collagen binding in both a static assay (CBA) and a flow-based assay at 2,500s−1 in which VWF is bound to collagen on a surface, and labeled platelet adhesion is quantified. The multimer profile of all the rmVWFs was normal. The expression level of the rmVWF derived from HEK293T cells was quantified. W1745C and the A3 deletion showed significantly lower levels of expression and the A1 deletion mutant showed strong intracellular retention. In the static collagen binding assay, S1731T showed almost normal binding to collagen type I and a 50% reduction in binding to collagen type III. The other 3 missense variants, W1745C, S1783A and H1786D, showed reduced binding to both collagens I and III, and the A3 deletion mutant showed absent binding. In the in vitro flow assay, the sensitivity to detect defects in collagen binding was superior to the static assay, although the patterns of binding defects were similar. W1745C showed similar low levels of platelet adhesion to both types of collagen, while S1783A and H1786D showed a lack of platelet binding on the collagen III surface similar to the A3 deletion mutant, and a reduced binding to collagen type I similar to W1745C. The gain-of-function mutant showed consistent enhanced collagen binding and platelet adhesion in the static and flow assays, respectively. In vivo studies delivered the mVWF cDNAs with a strong liver specific promoter by hydrodynamic injection. At 7 days post-delivery, the VWF:Ag levels in the WT and collagen binding variant mice were similar, apart from the W1745C mutant, that showed 14.6% levels compared to WT. Platelet counts and multimer patterns were normal with the collagen binding variants. In vivo intravital microscopy studies were performed using the cremaster arteriolar model when VWF levels were in a physiological range. Thrombosis was induced by 10%FeCl3 applied for 3 mins. Platelets were labeled in vivo by Rhodamine 6G and the thrombus development was analyzed by spinning disc confocal microscopy. Loss-of-function mutants showed transient platelet adhesion at the site of injury, however the adhesion was unstable and vessel occlusion was not observed. Using three complementary experimental systems we have been able to confirm the collagen binding defects in this group of variant VWFs. There is a differential sensitivity to the two forms of collagen and of the three experimental systems. The A3 deletion mutant consistently resulted in the most severe phenotype while the missense mutants showed variable degrees of functional deficit. Disclosures:No relevant conflicts of interest to declare.

In-vitro assessment of platelet function

Platelets (PLTs), play a key role in hemostasis, clot stability and retraction as well as in vascular repair and anti-microbial host defense. Upon vessel wall damage, PLTs undergo a highly regulated set including adhesion, spreading, aggregation, release reactions as well as exposure of procoagulant surfaces to rapidly form a hemostatic plug that occludes the site of damage. When PLT function is impaired, the bleeding risk increases, but (hyperreactive) PLTs are also involved in many pathophysiological events like thrombosis, vessel constriction, atherogenesis, tumor growth and metastasis, inflammation including atherosclerosis and the subsequent formation of arterial thrombi resulting in stroke and myocardial infarction. While hereditary PLT function disorders are very rare, acquired PLT function abnormalities occur in the course of many diseases and can be associated with many drugs, i.e., non-steroidal anti-inflammatorics, antibiotics or heparin. Therefore, apart from disease diagnosis, severity, and prognosis, assessment of PLT function also serves for identifying the efficacy of anti-PLT therapy and PLT hyperfunction as a possible predictor for thromboembolic events. Since PLTs undergo a lot of measurable changes during storage ex-vivo, one effort of transfusion medicine is the quality monitoring of PLT concentrates (PCs), but also the detection of donors with PLT dysfunction and the determination of patients in which PLT transfusions are effective. The majority of PLT tests focus only on PLT functions involved directly in hemostasis including adhesion/aggregation, coagulation, and clot retraction. Traditional tests, almost complex, time-consuming, and poorly specified, are meanwhile enriched by more user friendly and easy-to-use point-of-care tests on fully automated instruments within whole blood without the requirement of sample processing. These tests help identifying surgical patients at increased risk of post-operative bleeding or with resistance to anti-PLT therapy, therefore at increased risk of thromboembolism. However, up to now, no study shows real outcome benefits by including these tests into the disease management. To date, no function test is suitable to address all distinct steps of PLT activation or reliably predict PLT behavior in vivo following transfusion.

Inhibitors of the Platelet Thrombin Receptor

Not that long ago, aspirin, heparin, and warfarin were the only available antithrombotic agents for treating cardiovascular disease patients at risk of thrombotic events. These agents are still used in several places around the world, and it is remarkable how difficult it was to discover other agents that are more effective and/or safer. Since the mid-1980s we have been witnessing an explosion of research on new antithrombotic therapies, resulting in the availability of ticlopidine and clopidogrel (thienopyridine P2Y12-receptor inhibitors), low–molecular-weight heparins (eg, enoxaparin), and intravenous GPIIb/IIIa-receptor inhibitors (abciximab, eptifibatide, and tirofiban), later followed by fondaparinux (a synthetic indirect intravenous anti-Xa agent), bivalirudin (an intravenous direct anti-IIa agent), and more recently, prasugrel (a more potent thienopyridine) (Figure). Figure. The coagulation cascade, platelet activation pathways, and targets of antithrombotic agents. inhib indicates inhibition; LMWH, low–molecular-weight heparin; AT, antithrombin; vWF, von Willebrandt factor; TxA2, thromboxane A2; and ADP, adenosine diphosphate. Articles see pp 1843 and 1854 In the near future, several new oral antithrombotic agents may become available for treating patients with cardiovascular diseases: ticagrelor (the first direct reversible P2Y12 antagonist), dabigatran (an oral direct anti-IIa agent), rivaroxaban (an oral direct anti-Xa agent), and apixaban (also an oral direct anti-Xa agent). Other P2Y12 antagonists (eg, elinogrel) and oral anti-Xa agents (edoxaban, betrixaban, YM150, and TAK-442) are being studied or will be studied in phase-III programs (Figure). New antiplatelet therapies that target pathways not affected by aspirin or P2Y12-receptor antagonists could provide more comprehensive inhibition of platelet activation, and contribute to a greater inhibition of platelet-mediated thrombosis. Inhibition of protease-activated receptor-1 (PAR-1), a receptor for thrombin, is a new attractive approach in the development of better and safer antiplatelet therapy. As shown in the Figure, thrombin is the key effector of the coagulation cascade, but is also …

Cavitation inception and damage effects in liquid mercury exposed to a high-energy pulsed proton beam.

The Oak Ridge National Laboratory Spallation Neutron Source (SNS) employs a high-energy proton beam incident on a liquid mercury target to generate short bursts of neutrons. Concomitant with neutron production is the rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these bubbles may result in the premature erosion of the target’s steel walls. We report on a multi-pronged effort to both understand and address the problem by (1) inhibiting cavitation inception using bubble injection, (2) analyze cavitation and cavitation cloud dynamics using passive noise diagnostics, and (3) mitigating vessel wall damage using surface modification techniques. [Work supported by the ORNL Spallation Neutron Source, which is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy.]

Interaction with damaged vessel wall in vivo in humans induces platelets to express CD40L resulting in endothelial activation with no effect of aspirin intake

Activated platelets express CD40L on their plasma membrane and release the soluble fragment sCD40L. The interaction between platelet surface CD40L and endothelial cell CD40 leads to the activation of endothelium contributing to atherothrombosis. Few studies have directly demonstrated an increased expression of platelet CD40L in conditions of in vivo platelet activation in humans, and no data are available on its relevance for endothelial activation. We aimed to assess whether platelets activated in vivo at a localized site of vascular injury in humans express CD40L and release sCD40L, whether the level of platelet CD40L expression attained in vivo is sufficient to induce endothelial activation, and whether platelet CD40L expression is inhibited by aspirin intake. We used the skin-bleeding-time test as a model to study the interaction between platelets and a damaged vessel wall by measuring CD40L in the blood emerging from a skin wound in vivo in healthy volunteers. In some experiments, shed blood was analyzed before and 1 h after the intake of 500 mg of aspirin. Platelets from the bleeding-time blood express CD40L and release soluble sCD40L, in a time-dependent way. In vivo platelet CD40L expression was mild but sufficient to induce VCAM-1 expression and IL-8 secretion in coincubation experiments with cultured human endothelial cells. Moreover, platelets recovered from the bleeding-time blood activated endothelial cells; an anti-CD40L antibody blocked this effect. On the contrary, the amount of sCD40L released by activated platelets at a localized site of vascular injury did not reach the concentrations required to induce endothelial cell activation. Soluble monocyte chemoattractant protein-1, a marker of endothelium activation, was increased in shed blood and correlated with platelet CD40L expression. Aspirin intake did not inhibit CD40L expression by platelets in vivo. We concluded that CD40L expressed by platelets in vivo in humans upon contact with a damaged vessel wall activates endothelium; aspirin treatment does not inhibit this mechanism.

Genetic polymorphism of CYP11B2 gene and stroke intheHan Chinese population and a meta-analysis

The renin-angiotensin-aldosterone system is important for cerebrovascular research because it influences blood pressure, vasoconstriction, thrombosis, and vessel wall damage. We hypothesized that genetic variations in CYP11B2 gene might contribute to the susceptibility for stroke. Here, we present genetic association analyses on CYP11B2 gene variants in two independent ischemic stroke (IS) cohorts. Four single nucleotide polymorphisms (SNPs) from CYP11B2 gene were genotyped in 558 Chinese patients and 557 matched controls. Another replication was conducted in an independent sample of 525 IS cases and 694 controls. In addition, meta-analyses was performed to assess the association between the rs1799998 (-344C/T) CYP11B2 polymorphism and IS. Only one SNP rs1799998 (-344C/T)showed association with overall IS in the first study (P(dominant)=0.003, P(additive)=0.003, respectively), but this was not replicated in our second cohort. No associations were found for the rest of SNPs in both the studies. Meta-analyses (including our study) revealed that-344C/T of CYP11B2 was associated with IS both in a dominant effect (odds ratio=1.51, 95% CI: 1.06-2.16, P=0.023) and a recessive effect (odds ratio=1.57, 95% CI:1.14-2.16). Above all, our results suggest that genetic variation rs1799998 (-344C/T) of CYP11B2 gene may contribute to the risk of IS with moderate effect in Han Chinese population.

251 Renin-angiotensin-aldosterone system polymorphisms: a role or a hole in occurrence and long-term prognosis of acute myocardial infarction at Tunisian older people

Myocardial infarction (MI) is one of the major causes of death all over the world. Because MI frequently occurs suddenly without any preceding clinical symptoms, the prediction of MI is clinically of great importance. Angiotensin II is produced primarily by angiotensin I-converting enzyme (ACE) within atherosclerotic lesions and ACE level correlates with the severity of vessel wall damage. We analyzed the evolution with age of the frequencies of the I/D polymorphism of the ACE, A1166C of the angiotensin II AT1 receptor (AT1R), and M235T of the angiotensinogen (AGT) gene in a healthy population and he subsequent comparison to age- and sex-matched groups of MI patients. To investigate the influence of increasing age on the incidence and remaining lifetime risk of myocardial infarction in a cohort of older men. Polymorphisms of the AGT, ACE (I/D) and AGTR1 (A1166C) genes in patients and controls were analyzed using allele-specific PCR, and PCR-rflp. A total of 140 healthy subjects and 119 individuals with MI were divided into two groups < 65 and > 65 years old. The evolution with age showed that the AGT M allele (P < 0.001) and the ACE I allele (P < 0.05) frequency decreased with age. The TT genotype frequency increased in patients with MI > 65 years (OR = 3.52; 95% CI; 3.12–5.54). The AA genotype showed a similar behaviour (OR = 2.9; 95% CI; 1.11–5.6). The DD genotype increased in the MI > 65 group (OR = 6.66; 95% CI; 2.02–21.9). Serum ACE activity was positively associated to age (r = 0.38, p = 0.000). Patients with DD genotype > 65 years was significantly higher (119.7 ± 50.8 U/L) than in patients with DD genotype < 65 years (96.9 ± 31.4 U/L, p = 0.039). The incidence of new cardiovascular disease continued to increase after age 65 but was most often diagnosed at death. These findings suggest that people aged 60 and older have a substantial amount of undiagnosed disease. We propose that the study of the allele frequency evolution in an healthy population at different ages is essential to determine risk factors for MI in case-control studies.

Blood-brain barrier and cerebral small vessel disease

Increasing evidence from neuro and retinal imaging, neuropathology, epidemiology and experimental models suggests that the primary underlying initiating cause of cerebral small vessel disease is the derangement of the blood-brain barrier. This may start some years before the first symptoms, leads to the small vessel structural changes (vessel wall thickening, disorganisation and eventual breakdown) and perivascular changes (oedema, enlarged perivascular spaces, tissue damage interpreted as “infarcts”) and is fundamentally different to traditional “ischaemic” mechanisms, although small vessel occlusion due to thrombus formation on damaged vessel walls may be a late secondary phenomenon. Space limits a detailed discussion of the epidemiology and experimental evidence, so this brief review will focus on neuroimaging evidence and summarise the appearances, risk factors and associations of different components of cerebral small vessel disease as identified on imaging, discuss potential causes and, in particular, the evidence that disordered blood-brain barrier precipitates or worsens progression of cerebral small vessel disease. This mechanism may also play a role in other common disorders of ageing such as Alzheimer's disease.

Mental Stress, Arterial Stiffness, Central Pressures, and Cardiovascular Risk

To the Editor: We read with great interest the meta-analysis by Chida and Steptoe1 linking poor responses to mental stress with future cardiovascular (CV) risk. The authors eloquently present the pros and cons of laboratory tests that are used to provoke stress, highlight the importance of immediate response to stimuli, as well as of subsequent poststress recovery, and focus on published studies that present longitudinal data regarding CV risk of the subjects that were exposed to the stressor test. In longitudinal studies, the choice of end points and surrogate markers for assessing the effect of interventions is …

Percutaneous isolated liver perfusion with occlusion balloons and a catheter-based stent-graft-like perfusion device: an experimental study in a porcine model

To evaluate the feasibility and safety of a novel percutaneous isolated liver perfusion (PILP) system in a porcine model. The PILP catheter set, consisting of a portal vein and hepatic artery occlusion balloon and an hourglass-shaped vena cava stent-graft, was tested in six Dutch Landrace pigs. A veno-venous bypass between the distal portal vein and the right femoral vein, and isolated perfusion between the proximal portal vein and the hepatic veins were also created. Leak rate was determined using radioactivity measurement in the systemic circulation. Perfusion was then performed without (n = 2) or with cytotoxic drugs (n = 4). At the end of the procedure, all devices were retrieved and angiographic evaluation was performed of the involved vessel segments. In all pigs it was possible to insert, accurately position and retrieve all components of the PILP catheter set without angiographic signs of vessel-wall damage. Leakage rates to the systemic circulation were less than 7% over the course of the perfusion. In a porcine model, the PILP system can be safely and accurately positioned, and showed successful vascular isolation of the liver, with a leak rate to the systemic circulation of less than 7%.