The effects of purified eicosapentaenoic and docosahexaenoic acids on arterial thrombosis tendency and platelet function in rats.

Dietary eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were compared for their effects on arterial thrombus formation in vivo using a well validated rat model. Platelet aggregation (triggered by collagen or adenosine diphosphate in whole hirudinized blood), thromboxane formation (TxB2) and platelet phospholipid fatty acid composition were measured also. Animals fed diets containing hydrogenated coconut oil or sunflower seed oil served as pro- and anti-thrombotic controls, respectively. In a first study, rats were fed a mixture of EPA and DHA ethyl esters (MIX) in increasing amounts and results indicated that 4% of n-3 fatty acids had an optimum reducing effect on thrombosis tendency. Dietary administration of MIX further resulted in a dose-dependent promotion of disaggregation after collagen-induced aggregation, which significantly correlated with the reduction in platelet TxB2 formation. In a subsequent comparative study, both EPA and DHA ethyl esters affected thrombosis tendency, platelet aggregation and TxB2 formation to a similar extent. In addition, both polyenes increased the apparent thromboxane A2-sensitivity of platelets, which appeared negatively related to arterial thrombosis tendency. We conclude that EPA and DHA have similar reducing effects on arterial thrombogenesis in vivo in rats and have comparable effects on the selected platelet functions in vitro

Monitoring hypocoagulant conditions in rat plasma: factors determining the endogenous thrombin potential of tissue factor-activated plasma

SummaryAutomated human plasma, continuous monitoring of the formation and inactivation of thrombin during the coagulation process provides an adequate way to detect hypo- and hypercoagulant conditions. Here, we describe an analogous procedure to determine the endogenous thrombin potential (ETP), i. e. the free thrombin concentration-time integral, of coagulating rat plasma. When activated with tissue factor, the ETP of plasma from Wistar rats was comparable to the ETP of human plasma, in spite of a relatively short half-life time of free thrombin in rat plasma. The ETP was highly sensitive to heparin as well as to administration of vitamin K antagonist or feeding of the animals with a vitamin K-deficient diet. In plasma that was activated under sub-optimal conditions (reduced levels of tissue factor or vitamin K-dependent coagulation factors), the ETP increased with the rate of thrombin formation in the first minutes of the coagulation process. Since both parameters are dependent of the prothrombin concentration, it appears that this level plays an important role in determining both the initial and total activity of the coagulation system. Thus, automated measurement of free thrombin during the coagulation process of rat plasma allows a detailed analysis of hypocoagulability in this animal model

Modulation of rat platelet activation by vessel wall-derived prostaglandin and platelet-derived thromboxane: effects of dietary fish oil on thromboxane-prostaglandin balance

Modulation of rat platelet activation by vessel wall-derived prostaglandin and platelet-derived thromboxane: effects of dietary fish oil on thromboxane-prostaglandin balance.Nieuwenhuys CM, Feijge MA, Offermans RF, Kester AD, Hornstra G, Heemskerk JW.Department of Human Biology, University of Maastricht, P.O. Box 616, 6200 MD, Maastricht, The Netherlands.By dietary manipulation of rats with n-3 polyunsaturated fatty acids (PUFAs), platelets and endothelium-containing aortic tissue were obtained with decreased levels of arachidonate and increased levels of eicosapentaenoate and docosahexaenoate. These diet-induced changes were accompanied by a reduced formation of thromboxane A(2) (TXA(2)) and prostaglandin I(2) (PGI(2)) in platelets and aortic tissue, respectively. When platelets were incubated with autologous, aorta-derived PGI(2), the dietary modulation of PGI(2) generation had a stronger effect on the activation process than the dietary effect on TXA(2) generation. The platelet-inhibiting effect of PGI(2) was independent of the type of agonist and involved both TXA(2)-dependent and -independent activation responses. PGI(2) also inhibited the agonist-induced formation of TXA(2). In addition, the platelet-inhibitory effect of PGI(2) was more prolonged in time than the brief, stimulatory effect of TXA(2). We conclude that, in the thromboxane-prostaglandin balance of platelet activation, PGI(2) plays a more prominent role than TXA(2). Furthermore, dietary n-3 PUFAs appear to influence platelet activation more by reducing formation of endothelial PGI(2) than by decreasing autocrine-produced TXA(2). Thus, in rats, the proposed antithrombotic effect of fish oil is unlikely to be caused by an altered thromboxane-prostaglandin balance.<br/

The procoagulant effect of thrombin on fibrin(ogen)-bound platelets.

Department of Human Biology, University of Maastricht, The Netherlands. In a final stage of activation, platelets become procoagulant because of the appearance of phosphatidylserine (PS) at the membrane outer surface. This PS exposure requires a rise in cytosolic [Ca(2+)](i), is accompanied by formation of membrane blebs, and stimulates the formation of thrombin from its precursor prothrombin. Here, we investigated whether thrombin, as a potent platelet agonist, can induce this procoagulant response in plasma-free platelets interacting with fibrin or fibrinogen through their integrin alpha(IIb)beta(3) receptors. First, in platelets that were stimulated to spread over fibrin or fibrinogen surfaces with adrenaline, addition of thrombin and CaCl(2) caused a potent Ca(2+) signal that in about 30% of the cells was accompanied by exposure of PS. At low doses, integrin alpha(IIb)beta(3) receptor antagonist (RGD peptide) inhibited platelet spreading as well as thrombin-evoked PS exposure. Second, in platelet-fibrinogen microaggregates that were preformed in the presence of adrenaline, thrombin/CaCl(2) induced PS exposure and bleb formation of about 35% of the cells. Third, a potent, thrombin-dependent stimulation of prothrombinase activity was measured in platelet suspensions that were incubated with a fibrin clot. These results indicate that, in the absence of coagulating plasma, thrombin is a moderate inducer of the procoagulant response of platelets, once integrin alpha(IIb)beta(3)-mediated interactions are stimulated (by adrenaline) and CaCl(2) is present

Hypocoagulant and lipid-lowering effects of dietary n-3 polyunsaturated fatty acids with unchanged platelet activation in rats

We investigated the effects of dietary polyunsaturated fatty acids (PUFAs) on blood lipids and processes that determine hemostatic potential: platelet activation, coagulation, and fibrinolysis. For 8 to 10 weeks, Wistar rats were fed a high-fat diet containing various amounts (2% to 16%) of n-3 PUFAs derived from fish oil (FO) or a diet enriched in n-6 PUFAs from sunflower seed oil (SO). Only the FO diets caused a reduction in mean platelet volume, platelet arachidonate level, and formation of thromboxane B2 by activated platelets, but neither of the diets had a measurable effect on platelet activation. The FO-rich diets decreased the plasma concentrations of triglycerides and cholesterol, whereas the SO diet reduced triglycerides only. Parameters of fibrinolysis and standard coagulation times, ie, activated partial thromboplastin time and prothrombin time, were only marginally influenced by these diets. In contrast, dietary FO, but not SO, led to decreased levels of the vitamin K-dependent coagulation factors prothrombin and factor VII, while the level of antithrombin III was unchanged. The endogenous thrombin potential (ETP) was measured with an assay developed to detect the hypocoagulable state of plasma. After activation with tissue factor and phospholipids, the ETP was reduced by 23% or more in plasma from animals fed a diet with >4% FO. No significant effect of the SO diet on ETP was observed. Control experiments with plasma from warfarin-treated rats indicated that the ETP was more sensitive to changes in prothrombin concentration than in factor VII concentration. Taken together, these results indicate that in rats, prolonged administration of n-3 but not n-6 PUFAs can lead to a hypocoagulable state of plasma through a reduced capacity of vitamin K-dependent thrombin generation, with unchanged thrombin inactivation by antithrombin III

A Prospective Cohort Study on the Effects of Geriatric Rehabilitation Following Acute Exacerbations of COPD

OBJECTIVES: Older patients with chronic obstructive pulmonary disease (COPD),hospitalized for an acute exacerbation, often do not receive recommendedpost-acute pulmonary rehabilitation. This underuse might be related to theimpaired clinical and functional status of these patients, who are more likely topresent with frailty, comorbidities, and disability. Having developed andimplemented a geriatric rehabilitation program for these patients (GR_COPD), theprimary aim of this study was to investigate the effectiveness of this program.DESIGN AND INTERVENTION: A prospective cohort study with a 3-month follow-upperiod. Patients who declined the GR_COPD program were considered as controls.SETTING AND PARTICIPANTS: The study was conducted at the pulmonary department of2 hospitals. Patients were eligible when hospitalized as a result of an acuteexacerbation of COPD and indicated for the GR_COPD program based on standardizedcriteria.METHODS: Primary outcome was defined as change in disease-specific health statusmeasured with the clinical COPD questionnaire (CCQ), secondary outcome as theexacerbation rate ratio during follow-up. To balance potential confoundersbetween the intervention and control group, propensity score-based weightedlinear regression analyses were performed.RESULTS: Of the 158 included patients [78 (49.4%) male, mean age 70.8 (±8.1)years, mean forced expiratory volume in 1 second: 35.5 (±12.8) as % ofpredicted], 78 received the GR_COPD program. The results of the CCQ showed asignificant and clinically relevant treatment effect of -0.56 points [95%confidence interval (CI) -0.89, -0.23; P = .001). Patients in the control grouphad 2.77 times more exacerbations compared with the intervention group (95% CI2.13, 3.58; P CONCLUSIONS/IMPLICATIONS: This study shows a clinically relevant effect of theGR_COPD program on disease-specific health status and exacerbation rate.Implementation of the program for older patients with severe COPD hospitalizedfor an acute exacerbation is recommended.Development and application of statistical models for medical scientific researc