Glycoprotein Ib clustering in platelets can be inhibited by α-linolenic acid as revealed by cryo-electron tomography.

Platelet adhesion to the sub-endothelial matrix and damaged endothelium occurs through a multi-step process mediated in the initial phase by glycoprotein Ib binding to von Willebrand factor (vWF), which leads to the subsequent formation of a platelet plug. The plant-derived ω-3 fatty acid α-linolenic acid is an abundant alternative to fish-derived n-3 fatty acids and has anti-inflammatory and antithrombotic properties. In this study, we investigated the impact of α-linolenic acid on human platelet binding to vWF under high-shear flow conditions (mimicking blood flow in stenosed arteries). Pre-incubation of fresh human blood from healthy donors with α-linolenic acid at dietary relevant concentrations reduced platelet binding and rolling on vWF-coated microchannels at a shear rate of 100 dyn/cm2 Depletion of membrane cholesterol by incubation of platelet-rich plasma with methyl-ß cyclodextrin abrogated platelet rolling on vWF. Analysis of glycoprotein Ib by applying cryo-electron tomography to intact platelets revealed local clusters of glycoprotein Ib complexes upon exposure to shear force: the formation of these complexes could be prevented by treatment with α-linolenic acid. This study provides novel findings on the rapid local rearrangement of glycoprotein Ib complexes in response to high-shear flow and highlights the mechanism of in vitro inhibition of platelet binding to and rolling on vWF by α-linolenic acid.

Amotosalen/ultraviolet A pathogen inactivation technology reduces platelet activatability, induces apoptosis and accelerates clearance.

Amotosalen and ultraviolet A (UVA) photochemical-based pathogen reduction using the Intercept™ Blood System (IBS) is an effective and established technology for platelet and plasma components, which is adopted in more than 40 countries worldwide. Several reports point towards a reduced platelet function after Amotosalen/UVA exposure. The study herein was undertaken to identify the mechanisms responsible for the early impairment of platelet function by the IBS. Twenty-five platelet apheresis units were collected from healthy volunteers following standard procedures and split into 2 components, 1 untreated and the other treated with Amotosalen/UVA. Platelet impedance aggregation in response to collagen and thrombin was reduced by 80% and 60%, respectively, in IBS-treated units at day 1 of storage. Glycoprotein Ib (GpIb) levels were significantly lower in IBS samples and soluble glycocalicin correspondingly augmented; furthermore, GpIbα was significantly more desialylated as shown by Erythrina Cristagalli Lectin (ECL) binding. The pro-apoptotic Bak protein was significantly increased, as well as the MAPK p38 phosphorylation and caspase-3 cleavage. Stored IBS-treated platelets injected into immune-deficient nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice showed a faster clearance. We conclude that the IBS induces platelet p38 activation, GpIb shedding and platelet apoptosis through a caspase-dependent mechanism, thus reducing platelet function and survival. These mechanisms are of relevance in transfusion medicine, where the IBS increases patient safety at the expense of platelet function and survival.

Intravenously administered APAC, a dual AntiPlatelet AntiCoagulant, targets arterial injury site to inhibit platelet thrombus formation and tissue factor activity in mice.

INTRODUCTION: Arterial thrombosis is the main underlying mechanism of acute atherothrombosis. Combined antiplatelet and anticoagulant regimens prevent thrombosis but increase bleeding rates. Mast cell-derived heparin proteoglycans have local antithrombotic properties, and their semisynthetic dual AntiPlatelet and AntiCoagulant (APAC) mimetic may provide a new efficacious and safe tool for arterial thrombosis. We investigated the in vivo impact of intravenous APAC (0.3-0.5 mg/kg; doses chosen according to pharmacokinetic studies) in two mouse models of arterial thrombosis and the in vitro actions in mouse platelets and plasma. MATERIALS AND METHODS: Platelet function and coagulation were studied with light transmission aggregometry and clotting times. Carotid arterial thrombosis was induced either by photochemical injury or surgically exposing vascular collagen after infusion of APAC, UFH or vehicle. Time to occlusion, targeting of APAC to the vascular injury site and platelet deposition on these sites were assessed by intra-vital imaging. Tissue factor activity (TF) of the carotid artery and in plasma was captured. RESULTS: APAC inhibited platelet responsiveness to agonist stimulation (collagen and ADP) and prolonged APTT and thrombin time. After photochemical carotid injury, APAC-treatment prolonged times to occlusion in comparison with UFH or vehicle, and decreased TF both in carotid lysates and plasma. Upon binding from circulation to vascular collagen-exposing injury sites, APAC reduced the in situ platelet deposition. CONCLUSIONS: Intravenous APAC targets arterial injury sites to exert local dual antiplatelet and anticoagulant actions and attenuates thrombosis upon carotid injuries in mice. Systemic APAC provides local efficacy, highlighting APAC as a novel antithrombotic to reduce cardiovascular complications.

Dietary alpha-linolenic acid reduces platelet activation and collagen-mediated cell adhesion in sickle cell disease mice.

BACKGROUND: Sickle cell disease (SCD) is a genetic hemoglobinopathy associated with high morbidity and mortality. The primary cause of hospitalization in SCD is vaso-occlusive crisis (VOC), mediated by alteration of red blood cells, platelets, immune cells and a pro-adhesive endothelium. OBJECTIVES: We investigated the potential therapeutic use of the plant-derived omega-3 alpha-linolenic acid (ALA) in SCD. METHODS: Berkeley mice were fed a low- or high-ALA diet for 4 weeks, followed by analysis of liver fibrosis, endothelial activation, platelet activation and formation of platelet-neutrophils aggregates. Aggregation of platelets over collagen under flow after high-ALA was compared to a blocking P-selectin Fab. RESULTS: Dietary high-ALA was able to reduce the number of sickle cells in blood smear, liver fibrosis, and the expression of adhesion molecules on the endothelium of aorta, lungs, liver and kidneys (VCAM-1, ICAM-1 and vWF). Specific parameters of platelet activation were blunted after high-ALA feeding, notably P-selectin exposure and the formation of neutrophil-platelet aggregates, along with a correspondingly reduced expression of PSGL-1 on neutrophils. By comparison, in vivo treatment of SCD mice with the anti-P-selectin Fab was able to similarly reduce the formation of neutrophil-platelet aggregates, but did not reduce GpIbα shedding nor the activation of the αIIb ß3 integrin in response to thrombin. Both ALA feeding and P-selectin blocking significantly reduced collagen-mediated cell adhesion under flow. CONCLUSIONS: Dietary ALA is able to reduce the pro-inflammatory and pro-thrombotic state occurring in the SCD mouse model and may represent a novel, inexpensive and readily available therapeutic strategy for SCD.

Lifelong dietary omega-3 fatty acid suppresses thrombotic potential through gut microbiota alteration in aged mice.

Aging is a major risk factor for cardiovascular diseases, including thrombotic events. The gut microbiota has been implicated in the development of thrombotic risk. Plant-derived omega-3 fatty acid ɑ-linolenic acid (ALA) confers beneficial anti-platelet and anti-inflammatory effects. Hence, antithrombotic activity elicited by ALA may be partly dependent on its interaction with gut microbiota during aging. Here, we demonstrate that lifelong dietary ALA decreases platelet hyperresponsiveness and thrombus formation in aged mice. These phenotypic changes can be partly attributed to alteration of microbial composition and reduction of its metabolite trimethylamine N-oxide and inflammatory mediators including TNF-α, as well as the upregulated production of short-chain fatty acid acetate. ALA-rich diet also dampens secretion of increased procoagulant factors, tissue factor and plasminogen activator inhibitor-1, in aged mice. Our results suggest long-term ALA supplementation as an attractive, accessible, and well-tolerated nutritional strategy against age-associated platelet hyperreactivity and thrombotic potential.

Long-term dietary supplementation with plant-derived omega-3 fatty acid improves outcome in experimental ischemic stroke.

BACKGROUND AND AIMS: Early revascularization -the gold standard therapy for ischemic stroke- is often withheld in the elderly population due to high risk of complications. Thus, safe and effective preventive and therapeutic options are needed. The plant-derived omega-3-fatty-acid alpha-linolenic-acid (ALA) has emerged as a novel cardiovascular-protective agent. As of yet, little is known about its potential therapeutic effects on stroke. We hereby aimed to investigate the impact of a clinically relevant long-term dietary intervention with ALA on stroke outcome. METHODS: Six month-old C57BL/6 wildtype males were either fed an ALA-rich (high ALA) or a control diet (low ALA) for 12 months. At 18 months, brain ischemia/reperfusion was induced by transient middle cerebral artery occlusion (tMCAO). Stroke size and neurological function were assessed. Functional blood-brain-barrier-(BBB) permeability and protein expression were assessed by immunohistochemistry. Baseline inflammatory markers were measured at 18 months. RESULTS: High ALA-fed animals displayed decreased circulating TNF-α levels and Neutrophil-to-Lymphocyte Ratios at 18 months. Stroke size and neurological dysfunction were significantly reduced in high ALA-fed animals. Coherently to the reduced stroke size, functional BBB integrity and occludin endothelial expression were maintained by high ALA supplementation. Additionally, ALA reduced endothelial activation and thus recruitment and activation of macrophages and resident microglia. Finally, high ALA diet reduced the expression of BBB-degrading and neurotoxic MMP-3 and MMP-9. CONCLUSIONS: We demonstrate the beneficial effects of a clinically relevant and feasible dietary intervention with a safe and readily available compound in the setting of stroke. The protective effects observed with ALA supplementation may relate to blunting of inflammation and might pave the way for novel stroke treatments.

Gut microbiota-dependent trimethylamine-N-oxide (TMAO) shows a U-shaped association with mortality but not with recurrent venous thromboembolism.

INTRODUCTION: Gut microbiota-dependent trimethylamine-N-oxide (TMAO) correlates with arterial thrombotic events including myocardial infarction and stroke, and mortality. However, the association of TMAO with recurrent venous thromboembolism (VTE) and mortality remains unknown. METHODS: TMAO plasma levels were assessed by high performance liquid chromatography in 859 patients aged ≥65 years with acute VTE and categorized into low (<2.28 µmol/L), medium (2.28-6.57 µmol/L), and high levels (>6.57 µmol/L) based on the 25th and 75th percentile. Associations of TMAO with recurrent VTE, major or non-major bleeding, and mortality were investigated. RESULTS: During a mean follow-up of 28 months, 106 patients developed recurrent VTE, 259 had major or non-major bleeding events, and 179 patients died. The risk of recurrent VTE did not differ significantly between patients with low, medium (adjusted subhazard ratio [SHR], 1.38; 95% confidence interval [CI], 0.81 to 2.36; p = 0.232) and high TMAO levels (SHR, 1.44; 95% CI, 0.80 to 2.58, p = 0.221). Compared with low TMAO levels, the adjusted hazard ratio [HR] for mortality was 0.68 (95% CI, 0.47 to 0.98, p = 0.039) in patients with medium TMAO levels and 1.02 (95% CI, 0.68 to 1.52, p = 0.922) in patients with high TMAO levels. Fractional polynomial Cox-regression confirmed a U-shaped association (adjusted p = 0.045), with the lowest mortality risk in patients with TMAO around 4 µmol/L. TMAO was not associated with major or non-major bleeding. CONCLUSION: TMAO showed a U-shaped association with mortality in elderly patients with acute VTE and was not associated with recurrent VTE and major or non-major bleeding.

Whole blood omega-3 fatty acid concentrations are inversely associated with blood pressure in young, healthy adults.

BACKGROUND: Omega-3 fatty acids (n - 3 FA) may have blood pressure (BP)-lowering effects in untreated hypertensive and elderly patients. The effect of n - 3 FA on BP in young, healthy adults remains unknown. The Omega-3 Index reliably reflects an individuals' omega-3 status. We hypothesized that the Omega-3 Index is inversely associated with BP levels in young healthy adults. METHODS: The current study (n = 2036) is a cross-sectional study investigating the baseline characteristics of a cohort, which includes healthy adults, age 25-41 years. Individuals with cardiovascular disease, known diabetes or a BMI higher than 35 kg/m were excluded. The Omega-3 Index was determined in whole blood using gas chromatography. Association with office and 24-h BP was assessed using multivariable linear regression models adjusted for potential confounders. RESULTS: Median Omega-3 Index was 4.58% (interquartile range 4.08; 5.25). Compared with individuals in the lowest Omega-3 Index quartile, individuals in the highest had a SBP and DBP that was 4 and 2 mmHg lower, respectively (P < 0.01). A significant linear inverse relationship of the Omega-3 Index with 24-h and office BP was observed. Per 1-U increase in log-transformed Omega-3 Index the lowering in BP (given as multivariable adjusted ß coefficients; 95% confidence interval) was -2.67 mmHg (-4.83; -0.51; P = 0.02) and -2.30 mmHg (-3.92; -0.68; P = 0.005) for 24-h SBP and DBP, respectively. CONCLUSION: A higher Omega-3 Index is associated with statistically significant, clinically relevant lower SBP and DBP levels in normotensive young and healthy individuals. Diets rich in n - 3 FA may be a strategy for primary prevention of hypertension.

Differences in Expression of DPP4 in Steatotic Rat Liver Are Not Related to Differences in the Methylation of its Gene Promoter.

The aim of the present study was to investigate the methylation status in the promoter region of Dipeptidyl peptidase-IV (Dpp4) gene, in livers from obese Zucker rats with different patterns of immunohistochemical positivity. Molecular analysis was carried-out on DNA obtained from livers of obese and lean Zucker rats and of control Wistar rats using the bisulfite conversion method and DNA sequencing. Our study focused on the genomic region of 1,000 bp, which includes the final part of 680 bp of the Dpp4 gene promoter and a small stretch of 320 bp at the beginning of the gene. The results indicate that the different immunohistochemical pattern of DPP4 observed in obese (fa/fa) and lean (fa/-) Zucker rats is not correlated to DNA methylation of its promoter. This is in agreement with the results of other studies carried-out on visceral and subcutaneous adipose tissue with varying levels of enzyme expression, in which differences in the methylation pattern of the Dpp4 promoter region were not observed.