Decreased platelet aggregation by shear stress-stimulated endothelial cells in vitro: description of a method and first results in diabetes.

The interaction between platelets and endothelium in vivo is a complex phenomenon. Our aim was to develop an in vitro system that mimics the in vivo environment and investigate platelet function in a common pathological condition. Human umbilical vein endothelial cells were used and platelets from 28 type 2 diabetes patients were studied under shear stress conditions. Mean coefficient of variation of platelet aggregation was 10% in dynamic conditions in the presence of endothelium. Endothelial cells increased the concentration of inductor needed to achieve 50% platelet aggregation to adenosine diphosphate from 2.6 ± 1.3 in static conditions to 3.7 ± 1.3 µM in dynamic conditions. A similar pattern was observed when collagen was used for platelet activation. Incubation of endothelium with a nitric oxide inhibitor abolished this effect, indicating platelet inhibitory effect of endothelial cells is nitric oxide mediated. Platelet reactivity of healthy controls was less influenced by the presence of endothelial cells and displayed reduced basal platelet reactivity compared with platelets from diabetes patients. We show that platelet aggregation in diabetes as commonly reported in vitro may not fully reflect the in vivo pathophysiological process. Future studies are warranted to investigate other pathological conditions and analyse the effects of antiplatelet agents using this system.

Triglyceride glucose index and common carotid wall shear stress.

OBJECTIVES: Alterations in wall shear stress contribute to both clinical and subclinical atherosclerosis. Several conditions such as hypertension, diabetes, and obesity can impair shear stress, but the role of insulin resistance has never been investigated. The present study was designed to investigate whether insulin resistance assessed by TyG Index associates with wall shear stress in the common carotid artery. METHODS: One hundred six individuals were enrolled. Blood pressure, lipids, glucose, and cigarette smoking were evaluated. TyG Index was calculated as log[fasting triglycerides × fasting glucose / 2]. Subjects underwent blood viscosity measurement and echo-Doppler evaluation of carotid arteries to calculate wall shear stress. The association between TyG Index and carotid wall shear stress was assessed by simple and multiple regression analyses. RESULTS: TyG Index was significantly and inversely associated with carotid wall shear stress both in simple (r = -0.44, P < 0.001) and multiple regression analyses accounting for age, sex, and major cardiovascular risk factors. The association was further confirmed after exclusion of subjects with diabetes, dyslipidemia, fasting blood glucose greater than 100 mg/dL, and triglycerides greater than 150 mg/dL. CONCLUSIONS: The present findings suggest that increasing insulin resistance, as assessed by TyG Index, associates with atherosclerosis-prone shear stress reduction in the common carotid artery.

The effect of HDL cholesterol on blood and plasma viscosity in healthy subjects.

OBJECTIVE: The influence of lipids on blood and plasma viscosity has not been fully elucidated. In this study we evaluated the contribution of HDL cholesterol to blood and plasma viscosity, in healthy subjects. METHODS: One hundred and forty-four (80 males and 64 females) subjects were enrolled among free-living participants to a cardiovascular disease screening. Exclusion criteria were: diabetes, elevated triglycerides, elevated LDL cholesterol, smoking and drug use. Blood lipids were measured by routine methods. Blood and plasma viscosity were measured by a cone-plate viscometer (Wells-Brookfield DV-III, Stoughton, U.S.A.). Subjects were divided in two groups: at low (<50 mg/dl) and high HDL cholesterol (>50 mg/dl). RESULTS: Blood and plasma viscosity were similar in subjects at low and high HDL cholesterol. In univariate analysis none of the lipid variables was significantly correlated with blood and/or plasma viscosity. In multivariate analysis only LDL cholesterol was marginally associated with blood viscosity. CONCLUSION: HDL cholesterol does not influence blood and plasma viscosity in healthy normolipidemic subjects. LDL cholesterol is marginally associated with blood viscosity.

Modulating the vascular behavior of metastatic breast cancer cells by curcumin treatment.

The spreading of tumor cells to secondary sites (tumor metastasis) is a complex process that involves multiple, sequential steps. Vascular adhesion and extravasation of circulating tumor cells (CTCs) is one, critical step. Curcumin, a natural compound extracted from Curcuma longa, is known to have anti-tumoral, anti-proliferative, anti-inflammatory properties and affect the expression of cell adhesion molecules, mostly by targeting the NF-κB transcription factor. Here, upon treatment with curcumin, the vascular behavior of three different estrogen receptor negative (ER(-)) breast adenocarcinoma cell lines (SK-BR-3, MDA-MB-231, MDA-MB-468) is analyzed using a microfluidic system. First, the dose response to curcumin is characterized at 24, 48, and 72 h using a XTT assay. For all three cell lines, an IC(50) larger than 20 µM is observed at 72 h; whereas no significant reduction in cell viability is detected for curcumin concentrations up to 10 µM. Upon 24 h treatment at 10 µM of curcumin, SK-BR3 and MDA-MB-231 cells show a decrease in adhesion propensity of 40% (p = 0.02) and 47% (p = 0.001), respectively. No significant change is documented for the less metastatic MDA-MB-468 cells. All three treated cell lines show a 20% increase in rolling velocity from 48.3 to 58.7 µm/s in SK-BR-3, from 64.1 to 73.77 µm/s in MDA-MB-231, and from 57.5 to 74.4 µm/s in MDA-MB-468. Collectively, these results suggest that mild curcumin treatments could limit the metastatic potential of these adenocarcinoma cell lines, possibly by altering the expression of adhesion molecules, and the organization and stiffness of the cell cytoskeleton. Future studies will elucidate the biophysical mechanisms regulating this curcumin-induced behavior and further explore the clinical relevance of these findings.