3.
Human CalDAG-GEFI gene (RASGRP2) mutation affects platelet function and causes severe bleeding.
Canault, M, Ghalloussi, D, Grosdidier, C, Guinier, M, Perret, C, Chelghoum, N, Germain, M, Raslova, H, Peiretti, F, Morange, PE, et al
The Journal of experimental medicine. 2014;(7):1349-62
-
-
Free full text
-
Abstract
The nature of an inherited platelet disorder was investigated in three siblings affected by severe bleeding. Using whole-exome sequencing, we identified the culprit mutation (cG742T) in the RAS guanyl-releasing protein-2 (RASGRP2) gene coding for calcium- and DAG-regulated guanine exchange factor-1 (CalDAG-GEFI). Platelets from individuals carrying the mutation present a reduced ability to activate Rap1 and to perform proper αIIbβ3 integrin inside-out signaling. Expression of CalDAG-GEFI mutant in HEK293T cells abolished Rap1 activation upon stimulation. Nevertheless, the PKC- and ADP-dependent pathways allow residual platelet activation in the absence of functional CalDAG-GEFI. The mutation impairs the platelet's ability to form thrombi under flow and spread normally as a consequence of reduced Rac1 GTP-binding. Functional deficiencies were confined to platelets and megakaryocytes with no leukocyte alteration. This contrasts with the phenotype seen in type III leukocyte adhesion deficiency caused by the absence of kindlin-3. Heterozygous did not suffer from bleeding and have normal platelet aggregation; however, their platelets mimicked homozygous ones by failing to undergo normal adhesion under flow and spreading. Rescue experiments on cultured patient megakaryocytes corrected the functional deficiency after transfection with wild-type RASGRP2. Remarkably, the presence of a single normal allele is sufficient to prevent bleeding, making CalDAG-GEFI a novel and potentially safe therapeutic target to prevent thrombosis.
4.
Effectiveness of clopidogrel dose escalation to normalize active metabolite exposure and antiplatelet effects in CYP2C19 poor metabolizers.
Horenstein, RB, Madabushi, R, Zineh, I, Yerges-Armstrong, LM, Peer, CJ, Schuck, RN, Figg, WD, Shuldiner, AR, Pacanowski, MA
Journal of clinical pharmacology. 2014;(8):865-73
-
-
Free full text
-
Abstract
Carriers of two copies of the loss-of-function CYP2C19*2 variant convert less clopidogrel into its active metabolite, resulting in diminished antiplatelet responses and higher cardiovascular event rates. To evaluate whether increasing the daily clopidogrel dose in poor metabolizers (PM) overcomes the effect of the CYP2C19 * 2 variant, we enrolled 18 healthy participants in a genotype-stratified, multi-dose, three-period, fixed-sequence crossover study. Six participants with the *1/*1 extensive (EM), *1/*2 intermediate (IM), and *2/*2 poor metabolizer genotypes each received 75 mg, 150 mg, and 300 mg each for 8 days. In each period, maximal platelet aggregation 4 hours post-dose (MPA4) and active metabolite area under the curve (AUC) differed among genotype groups (P < .05 for all). At day 8, PMs needed 300 mg daily and IMs needed 150 mg daily to attain a similar MPA4 as EMs on the 75 mg dose (32.6%, 33.2%, 31.3%, respectively). Similarly, PMs needed 300 mg daily to achieve active metabolite concentrations that were similar to EMs on 75 mg (AUC 37.7 and 33.5 ng h/mL, respectively). These results suggest that quadrupling the usual clopidogrel dose might be necessary to overcome the effect of poor CYP2C19 metabolism.
5.
Laropiprant attenuates EP3 and TP prostanoid receptor-mediated thrombus formation.
Philipose, S, Konya, V, Lazarevic, M, Pasterk, LM, Marsche, G, Frank, S, Peskar, BA, Heinemann, A, Schuligoi, R
PloS one. 2012;(8):e40222
Abstract
The use of the lipid lowering agent niacin is hampered by a frequent flush response which is largely mediated by prostaglandin (PG) D(2). Therefore, concomitant administration of the D-type prostanoid (DP) receptor antagonist laropiprant has been proposed to be a useful approach in preventing niacin-induced flush. However, antagonizing PGD(2), which is a potent inhibitor of platelet aggregation, might pose the risk of atherothrombotic events in cardiovascular disease. In fact, we found that in vitro treatment of platelets with laropiprant prevented the inhibitory effects of PGD(2) on platelet function, i.e. platelet aggregation, Ca(2+) flux, P-selectin expression, activation of glycoprotein IIb/IIIa and thrombus formation. In contrast, laropiprant did not prevent the inhibitory effects of acetylsalicylic acid or niacin on thrombus formation. At higher concentrations, laropiprant by itself attenuated platelet activation induced by thromboxane (TP) and E-type prostanoid (EP)-3 receptor stimulation, as demonstrated in assays of platelet aggregation, Ca(2+) flux, P-selectin expression, and activation of glycoprotein IIb/IIIa. Inhibition of platelet function exerted by EP4 or I-type prostanoid (IP) receptors was not affected by laropiprant. These in vitro data suggest that niacin/laropiprant for the treatment of dyslipidemias might have a beneficial profile with respect to platelet function and thrombotic events in vascular disease.
6.
Platelet aggregability in patients with hypertension treated with angiotensin II type 1 receptor blockers.
Sato, Y, Fujii, S, Imagawa, S, Ohmura, K, Ohmura, Y, Andoh, Y, Dong, J, Ishimori, N, Furumoto, T, Tsutsui, H
Journal of atherosclerosis and thrombosis. 2007;(1):31-5
Abstract
AIM: Cardiovascular events associated with hypertension often involve thrombosis. Increased platelet activity is one of the risk factors of cardiovascular diseases. Antithrombotic properties of antihypertensive agents are not fully characterized. Angiotensin II type 1 receptor blockers (ARBs) are widely used for the treatment of hypertension. Some ARBs can provoke antiaggregatory effects on platelets in vitro. Whether ARBs can inhibit platelet aggregation was tested in hypertensive patients in vivo. METHODS Platelet aggregation was assessed by the highly sensitive particle counting method using laser-light scattering. RESULTS Large platelet aggregation induced by adenosine diphosphate (ADP, 3 microM) was 2.6+/-0.4 (x10(7)) (SE) in hypertensive patients treated with losartan (72+/-3 years old, n=10) while it was 3.9+/-0.6 in hypertensive patients treated with candesartan (70+/-5 years old, n=6; p=0.056). Large platelet aggregation induced by thromboxane A2 receptor agonist, U46619 (10 microM), was 2.8+/-0.5 (x10(7)) in hypertensive patients treated with losartan while it was 5.1+/-0.9 in hypertensive patients treated with candesartan (p=0.033). Clinical characteristics including the control of blood pressure did not differ between the two groups (losartan 136+/-5/73+/-3 mmHg vs. candesartan 135+/-4/76+/-5). CONCLUSION Thus, losartan may have the possibility to inhibit platelet activation in patients with hypertension independent of blood pressure reduction. Antiaggregatory properties may be independent of angiotensin II type 1 receptor or of antihypertensive actions. The favorable effects of losartan on reduction of adverse cardiovascular events among hypertensive patients may be at least partly mediated by inhibition of platelet activation.
7.
Effects of atenolol and propranolol on platelet aggregation in moderate essential hypertension: randomized crossover trial.
Punda, A, Polić, S, Rumboldt, Z, Bagatin, J, Marković, V, Lukin, A
Croatian medical journal. 2005;(2):219-24
Abstract
AIM: To compare the effects of a selective beta-blocker atenolol and a nonselective beta-blocker propranolol on platelet aggregation. METHODS Twenty successive outpatients with moderate essential hypertension (6 women and 14 men, mean age-/+standard deviation 42.6-/+8.5 years) were randomized to either propranolol (40 mg three times a day) or atenolol (100 mg once a day) for the first two weeks, followed by a one-day washout period, and then a two-week administration of the alternative drug. Along with standard examinations and tests, circulating platelet aggregates were measured. RESULTS There were no significant differences in creatinine, blood glucose, potassium, total cholesterol, hemoglobin, red blood cells (RBC), or platelets in three periods: baseline, atenolol, and propranolol period. Significant and comparable reductions in systolic and diastolic arterial pressure, body weight, heart rate, and HDL-cholesterol were recorded in both patient groups. The LDL-cholesterol concentration increased significantly in propranolol compared with both baseline and atenolol period. Serum triglycerides increased significantly with both medications. The number of circulating platelet aggregates decreased significantly with propranolol (0.99-/+0.19) in comparison with both atenolol (1.41-/+0.70; P=0.004, Wilcoxon matched pairs test) and baseline (1.59-/+0.94; P=0.002, Wilcoxon matched pairs test). CONCLUSION Propranolol inhibits platelet aggregation more than atenolol and may have a favorable effect on the management of hypertension especially in patients with increased cardiovascular risk.
8.
Ingestion of quercetin inhibits platelet aggregation and essential components of the collagen-stimulated platelet activation pathway in humans.
Hubbard, GP, Wolffram, S, Lovegrove, JA, Gibbins, JM
Journal of thrombosis and haemostasis : JTH. 2004;(12):2138-45
-
-
Free full text
-
Abstract
BACKGROUND Quercetin, a flavonoid present in the human diet, which is found in high levels in onions, apples, tea and wine, has been shown previously to inhibit platelet aggregation and signaling in vitro. Consequently, it has been proposed that quercetin may contribute to the protective effects against cardiovascular disease of a diet rich in fruit and vegetables. OBJECTIVES A pilot human dietary intervention study was designed to investigate the relationship between the ingestion of dietary quercetin and platelet function. METHODS Human subjects ingested either 150 mg or 300 mg quercetin-4'-O-beta-D-glucoside supplement to determine the systemic availability of quercetin. Platelets were isolated from subjects to analyse collagen-stimulated cell signaling and aggregation. RESULTS Plasma quercetin concentrations peaked at 4.66 microm (+/- 0.77) and 9.72 microm (+/- 1.38) 30 min after ingestion of 150-mg and 300-mg doses of quercetin-4'-O-beta-D-glucoside, respectively, demonstrating that quercetin was bioavailable, with plasma concentrations attained in the range known to affect platelet function in vitro. Platelet aggregation was inhibited 30 and 120 min after ingestion of both doses of quercetin-4'-O-beta-D-glucoside. Correspondingly, collagen-stimulated tyrosine phosphorylation of total platelet proteins was inhibited. This was accompanied by reduced tyrosine phosphorylation of the tyrosine kinase Syk and phospholipase Cgamma2, components of the platelet glycoprotein VI collagen receptor signaling pathway. CONCLUSIONS This study provides new evidence of the relatively high systemic availability of quercetin in the form of quercetin-4'-O-beta-D-glucoside by supplementation, and implicates quercetin as a dietary inhibitor of platelet cell signaling and thrombus formation.
9.
Isosorbide dinitrate inhibits platelet adhesion and aggregation in nonthrombolyzed patients with acute myocardial infarction.
Gebalska, J, Wolk, R, Ceremuzynski, L
Clinical cardiology. 2000;(11):837-41
Abstract
BACKGROUND Apart from their vasodilatatory properties, nitrates have been shown to inhibit platelet aggregation. The effects of nitrates on platelet adhesion have not been studied. Nonselected patients with acute myocardial infarction (AMI) have been suggested to gain no benefit from administration of nitrates. However, the importance of nitrates may be greater in a subgroup of nonthrombolyzed patients with AMI. HYPOTHESIS Isosorbide dinitrate (ISDN) decreases platelet adhesion and aggregation in nonthrombolyzed patients with AMI. METHODS Consecutive 48 men with AMI, not eligible for thrombolytic therapy because of late presentation (> 12 h), were prospectively randomized 2:1 to double-blind ISDN (mean dose 2.4 +/- 0.9 mg/h) (n = 33) or placebo (0.9% sodium chloride) (n = 15) infusion. All patients received aspirin. Blood samples were taken at baseline (no study medication) and 3 h into ISDN or placebo infusion. Platelet adhesion to collagen was measured in the ethylene diamine tetraacetic acid (EDTA)-platelet rich plasma by recording changes in light transmission with an optical aggregometer. Platelet aggregation was measured using the Born's method. RESULTS Isosorbide dinitrate significantly decreased both platelet adhesion and aggregation. No effect was seen in the placebo group. CONCLUSIONS In patients with AMI who do not receive thrombolytic therapy, ISDN effectively inhibits platelet adhesion and aggregation. These effects of nitrates may be of therapeutic and prognostic significance in this group of patients.
10.
Fast platelet suppression by lysine acetylsalicylate in chronic stable coronary patients. Potential clinical impact over regular aspirin for coronary syndromes.
Gurfinkel, EP, Altman, R, Scazziota, A, Heguilen, R, Mautner, B
Clinical cardiology. 2000;(9):697-700
Abstract
BACKGROUND The rapid utilization of fibrinolytics following Q-wave myocardial infarction has clearly modified the evolution of this disease. However, it is still not known whether the immediate inhibition of platelet aggregation (PA) during the coronary event improves outcomes. HYPOTHESIS The present study was designed to test, in patients with known coronary artery disease (chronic stable angina), whether the particular kinetic pattern of lysine acetylsalicylate (LA) compared with aspirin may affect the time to onset of inhibition of platelet aggregation. METHODS Ten patients suffering from chronic stable angina participated in this study to compare the efficacy and speed of the inhibition of PA with 320 mg of LA versus 320 mg of aspirin. All patients discontinued the use of aspirin and any other anti-inflammatory agents for 15 days prior to the beginning of the study. They were randomly assigned to LA or aspirin. Blood specimens were obtained to measure the PA at admission, and 5, 10, 20, 30, and 60 min after ingestion. Patients continued to take the assigned drug once a day for the following 4 days. On Day 5, a new blood sample was taken. After this, patients underwent a 15-day wash-out period, and then crossed over to the opposite drug. The samples were analyzed immediately using platelet-rich plasma stimulated with adenosine diphosphate (ADP) 2 mumol/l, collagen 1 microgram/ml, epinephrine 20 mumol/l, and sodium arachidonate acid 0.75 mm/l. RESULTS The same level of PA inhibition after 30 and 60 min of aspirin administration can be obtained with LA 5 min following ingestion (sodium arachidonate acid: LA: 16.3 +/- 25.9 vs. aspirin 57.6 +/- 8.2; p = 0.00014; collagen: LA 18.9 +/- 20.1 vs. aspirin 47.2 +/- 10.5; p = 0.00092; ADP: LA 27.3 +/- 18.4 vs. aspirin 39.7 +/- 21.8, p = 0.18; epinephrine: LA 22.0 +/- 9.9 vs. aspirin 55.4 +/- 10.9, p = 0.00002. CONCLUSIONS Platelet aggregation inhibition immediately following LA may have significant clinical implications for the treatment of coronary syndromes.