Rapid changes in the coagulant proteins on saphenous vein endothelium in response to arterial flow

Healthy endothelium provides a nonthrombogenic surface. In this study the authors investigated the effect of arterial flow on the saphenous vein endothelial expression of proteins controlling thrombosis. Human saphenous vein segments, freshly excised from patients, were placed in a validated in vitro circuit with flow conditions shown to simulate arterial or venous circulations. In separate experiments, placement of an external polytetrafluoroethylene (PTFE) stent was used to differentiate the effects of pulsatile wall deformation and shear stress, while addition of drugs to the vein perfusate allowed study of the role of ion channels in transducing the response of the vein to arterial flow. Endothelial concentrations of thrombomodulin, nitric oxide synthase, tissue factor, and tissue plasminogen activator were assessed by quantitative immunohistochemistry and Western blotting of endothelial cell lysates, in paired vein samples, in comparison to control proteins. Arterial flow conditions caused a rapid and significant reduction in the endothelial concentration of thrombomodulin: The immunostaining area decreased from 80.1 ± 7.0 to 48.3 ± 5.0 and 32.9 ± 3.0% at 45 and 90 minutes respectively, p = 0.01. These findings were confirmed by Western blotting. The reduction in thrombomodulin concentration was unaffected by eliminating vein wall deformation by placement of an external PTFE stent or by including the K+ channel blocker tetraethylammonium (TEA) in the vein perfusate. In contrast, thrombomodulin concentrations remained high when blockers of stretch-activated cation and calcium channels were included in the vein perfusate. The endothelial concentration of nitric oxide synthase increased after 90 minutes of arterial flow and this change was abolished when TEA was included in the vein perfusate. Arterial flow induced rapid changes in saphenous vein antithrombotic proteins. Different cation channels mediated the flow-induced changes in thrombomodulin and nitric oxide synthase

Arterial flow conditions downregulate thrombomodulin on saphenous vein endothelium

Background - The antithrombogenic properties of venous endothelium may be attenuated when vein is implanted in the arterial circulation. Such changes may facilitate thrombosis, which is the final common pathway for saphenous vein arterial bypass graft occlusion. Methods and Results - Using human saphenous vein in a validated ex vivo flow circuit, we investigated (1) the possibility that arterial flow conditions (mean pressure, 100 mm Hg, 90 cpm, ?200 mL/min) alter the concentration of proteins involved in regulating thrombosis at the vessel wall and (2) the influence of ion channel blockade on such effects. Concentrations of thrombomodulin and tissue factor were quantified by Western blotting (ratio of yon Willebrand factor staining) and immunohistochemistry (as a percentage of CD31-staining area). Thrombomodulin concentrations after 90 minutes of venous and arterial flow conditions were quantified by immunostaining (68.9±4.8% and 41.0±3.0% CD31, respectively; P<0.01) and by Western blotting (1.35±0.20 and 0.15±0.03 ratio of yon Willebrand factor, respectively; P<0.01). The ability of endothelial cells to generate activated protein C also decreased from 62±14 to 19±10 ng · min- 1 · 1000 cells-1 (P=0.01). The significant reduction in thrombomodulin was attenuated if calcium was removed from the perfusate but not by external vein stenting. Inclusion in the vein perfusate of drugs that reduce calcium entry (including Gd3+, to block stretch-activated ion channels, and nifedipine) abolished the reduction in thrombomodulin concentration observed after arterial flow conditions. In freshly excised vein, negligible concentrations of tissue factor were detected on the endothelium and concentrations did not increase after 90 minutes of arterial flow conditions, although the inclusion of nifedipine caused the immunostaining to increase from 3.0±0.4% to 8.5±0.7% CD31 (P<0.02). Conclusions - In saphenous vein endothelium exposed to arterial flow conditions, there is rapid downregulation of thrombomodulin, sufficient to limit protein C activation, by a calcium-dependent mechanism

Neurocognitive and Psychiatric Symptoms across Vascular Sample.

<p>AAA denotes abdominal aortic aneurysm; IC denotes intermittent claudication; RBANS denotes Repeatable Battery for the Assessment of Neuropsychological Status; # includes ‘widowed’ participants: </p><p>* p-value derived from univariate analysis for mean comparison of variables with three groups (age, education, marital status) and student t-test for comparison of means of variables with two groups (patient groups, gender): p-value = 0.031.</p

Basic socio-demographic and clinical characteristics of patients with AAA or Intermittent Claudication.

<p>SD denotes standard deviation; AAA denotes abdominal aortic aneurysm; IC denotes intermittent claudication; CHD denotes coronary heart disease; BMI denotes body mass index; CRP denotes C-Reactive Protein; # includes ‘widowed’ participants;</p><p>* p-value of Chi-square test for categorical data and two sample t-test for continuous data.</p

Impact of Serum Biomarkers on Memory Domains of Cognitive Function in Overall Sample.

†<p>Linear regression adjusted for age and education; beta = standardized beta-coefficient; CI = confidence interval;</p><p>*significant at p<0.05;</p><p>CRP: C-reactive protein; HB g/l: Haemoglobin g/l; Aortic dia: aortic diameter; TAG: Triglycerides; LDL: low density lipoprotein.</p

RBANS Single Cognitive Test and Summary Scores across Vascular Groups.

<p>AAA denotes abdominal aortic aneurysm; IC denotes intermittent claudication; RBANS denotes Repeatable Battery for the Assessment of Neuropsychological Status; SD denotes standard deviation; </p><p>† p-values derived from student t test for mean comparison across two groups (AAA vs IC); n.s. denotes not significant.</p

Flow diagram showing studies included.

<p>45 published studies assessing the association of <i>TGF-β</i> SNPs and CHD were identified by searching the MEDLINE database. Appraisal of the abstracts identified 10 articles eligible for full-text appraisal. From these, a further 2 articles were excluded, leaving 8 articles for inclusion in the systematic review. Six of these studies adopted a case-control design, and data from these were extracted for further assessment in the meta-analysis.</p

Forest plots detailing unadjusted odds ratios and 95% confidence intervals for the association between TGFβ1 rs1800469, rs1800470 and rs1800471 with end-stage CHD calculated using the dominant model of inheritance.

<p>The dotted line represents overall odds ratio calculated in the current meta-analysis for each SNP.</p

Heterogeneity analysis of combined effect size.

<p>Q, Cochran Q test; df, degrees of freedom; I², I² index.</p

Meta-analysis of published associations between <i>TGF-β1</i> SNPs and complications of CHD.

<p>OR, odds ratio; CI, 95% confidence intervals.</p><p>∼Rs1800468: promoter, in terms of minor A allele; ^±Rs1800469: promoter, in terms of minor T allele; ^§Rs1800470: coding sequence, in terms of minor T allele; ¤Rs1800471: coding sequence, in terms of minor C allele; °Rs1800472: coding sequence, in terms of minor T allele.</p>*<p>Combined, indicates meta-analysis data calculated for a Random Effects model, assuming dominant inheritance. Data for additive and recessive models displayed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037878#pone.0037878.s002" target="_blank">Table S1</a>.</p>†<p>Odds ratio given for combined male and female population, not just male population as provided by author.</p>‡<p>Odds ratio given in terms of minor allele, not major allele as stated in publication.</p