Amin Polzin

Release of sphingosine-1-phosphate from human platelets is dependent on thromboxane formation.

Summary.  Background: Platelets release the immune‐modulating lipid sphingosine‐1‐phosphate (S1P). However, the mechanisms of platelet S1P secretion are not fully understood. Objectives: The present study investigates the function of thromboxane (TX) for platelet S1P secretion during platelet activation and the consequences for monocyte chemotaxis. Methods: S1P was detected using thin‐layer chromatography in [3H]sphingosine‐labeled platelets and by mass spectrometry. Monocyte migration was measured in modified Boyden chamber chemotaxis assays. Results: Release of S1P from platelets was stimulated with protease‐activated receptor‐1‐activating peptide (PAR‐1‐AP, 100 μm). Acetylsalicylic acid (ASA) and two structurally unrelated reversible cyclooxygenase inhibitors diclofenac and ibuprofen suppressed S1P release. Oral ASA (500‐mg single dose or 100 mg over 3 days) attenuated S1P release from platelets in healthy human volunteers ex vivo. This was paralleled by inhibition of TX formation. S1P release was increased by the TX receptor (TP) agonist U‐46619, and inhibited by the TP antagonist ramatroban and by inhibitors of ABC‐transport. Furthermore, thrombin‐induced release of S1P was attenuated in platelets from TP‐deficient mice. Supernatants from PAR‐1‐AP‐stimulated human platelets increased the chemotactic capacity of human peripheral monocytes in a S1P‐dependent manner via S1P receptors‐1 and ‐3. These effects were inhibited by ASA‐pretreatment of platelets. Conclusions: TX synthesis and TP activation mediate S1P release after thrombin receptor activation. Inhibition of this pathway may contribute to the anti‐inflammatory actions of ASA, for example by affecting activity of monocytes at sites of vascular injury.

Antiplatelet effects of aspirin in chronic kidney disease patients

Essentials Chronic kidney disease (CKD) patients have a high risk of cardiovascular events. A pharmacodynamic evaluation of the effects of aspirin in 116 patients was carried out. The antiplatelet effects of aspirin are associated with impaired renal function. The optimal antithrombotic regimen in CKD patients must be investigated on a larger scale.

Prevention of dipyrone (metamizole) induced inhibition of aspirin antiplatelet effects

We have recently shown that dipyrone (metamizole), a non-opioid analgesic, can nullify aspirin (acetylsalicylic acid; ASA) antiplatelet effects in patients with coronary artery disease (CAD). In this study, we analysed the aspirin and dipyrone drug-drug interaction in order to identify strategies to prevent the dipyrone induced inhibition of asprin antiplatelet effects. Platelet function was measured by arachidonic acid-induced light-transmission aggregometry, thromboxane (TX) B2- formation by immunoassay. Dipyrone metabolite plasma levels were determined by high-performance-liquid-chromatography (HPLC). In seven healthy individuals, in vitro ASA (30 µM/ 100 µM/ 300 µM/ 1,000 µM) and dipyrone (10 µM) coincubation revealed, that the aspirin and dipyrone interaction can be overcome by increasing doses of aspirin. In 36 aspirin and dipyrone comedicated CAD patients, addition of ASA (30 µM/ 100 µM) in vitro inhibited, but did not completely overcome the dipyrone induced reduction of aspirin antiplatelet effects. Notably, the inhibition of thromboxane formation in aspirin and dipyrone comedicated CAD patients coincided with dipyrone plasma levels. In a cross-over designed study in four healthy individuals, we were able to prove that inhibition of aspirin (100 mg/ day) effects by dipyrone (750 mg/ day) was reversible. Furthermore, aspirin (100 mg/ day) medication prior to dipyrone (750 mg/ day) intake prevented the inhibition of antiplatelet effects by dipyrone in 12 healthy individuals. In conclusion, aspirin medication prior to dipyrone intake preserves antiplatelet effects, circumventing the pharmacodynamic drug-drug interaction at the level of cyclooxygenase-1.

High on-treatment platelet reactivity in transcatheter aortic valve implantation patients.

Dual antiplatelet therapy (DAPT) is recommended early after transcatheter aortic valve implantation (TAVI) procedure at the moment despite the lack of evidence. Two small randomized trials failed to demonstrate DAPT to be superior to aspirin alone in TAVI patients. However, it is known that there are substantial response variabilities to antiplatelet medication. We aimed to investigate high on-treatment platelet reactivity (HTPR), low on-treatment platelet reactivity (LTPR) to clopidogrel as well as HTPR to aspirin in patients undergoing TAVI procedure. We analyzed data of 140 TAVI patients in a real world observational study. Platelet function assays (clopidogrel-vasodilator-stimulated protein phosphorylation assay; aspirin-light-transmission aggregometry) have been performed during hospital course. Clinical complications were investigated during 30 days follow-up and defined using the valve academic research consortium standardized criteria. HTPR to clopidogrel occurred in 87 (62%) patients and LTPR in 9 (6.4%) patients. Aspirin antiplatelet effects were insufficient in 25 (18%) patients. Clinical complications were observed in 35 (25%) patients. Ischemic events occurred in 6 (4%), bleeding complications in 28 (20%) patients. There were no differences regarding the incidence of HTPR/LTPR in patients with overall complications, ischemic events or bleeding events. HTPR to clopidogrel is very frequent in TAVI patients. However bleeding complications are frequent and ischemic events are rare. Therefore, future clinical trials investigating the optimal antithrombotic regiment in TAVI patients should consider this high incidence of HTPR to clopidogrel and monitor clopidogrel antiplatelet effects carefully.

Aspirin inhibits release of platelet-derived sphingosine-1-phosphate in acute myocardial infarction

a Universitatsklinikum Dusseldorf, Klinik fur Kardiologie, Pneumologie und Angiologie, Universitatsstrase 1, 40225 Dusseldorf, Germany b Universitatsklinikum Dusseldorf, Institut fur Pharmakologie und Klinische Pharmakologie, Universitatsstrase 1, 40225 Dusseldorf, Germany c Universitat Potsdam, Institut fur Ernahrungswissenschaft, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany d Universitatsmedizin Greifswald, Institut fur Pharmakologie, Abteilung Allgemeine Pharmakologie, Felix-Hausdorff-Strase 3, 17487 Greifswald, Germany

Dabigatran enhances platelet reactivity and platelet thrombin receptor expression in patients with atrial fibrillation.

Essentials Whether or not dabigatran enhances the risk of myocardial infarction is under discussion. We measured platelet reactivity and thrombin receptor expression in dabigatran patients. Platelet reactivity and thrombin receptor expression is enhanced during dabigatran treatment. This should be considered when choosing the optimal direct oral anticoagulant for individuals.

Dipyrone comedication in aspirin treated stroke patients impairs outcome

BACKGROUND >50% of stroke patients rely on analgesic medication to control pain. Aspirin is the mainstay of medical treatment of stroke patients; however analgesic medication with dipyrone impairs aspirin antiplatelet effects ex-vivo. The clinical impact of this impairment is unknown. Therefore, we aimed to determine aspirin antiplatelet effects and neurological outcome in stroke patients with aspirin and dipyrone comedication. METHODS We conducted a prospective cohort study in 41 patients with stroke. Primary outcome was pharmacodynamic response to aspirin in dipyrone treated stroke patients. Secondary outcome was neurological recovery after stroke. Pharmacodynamic response to aspirin was measured using arachidonic acid induced aggregation in light-transmission aggregometry. Neurological outcome was determined three months after stroke onset by telephone interview. RESULTS Patients characteristics were similar in the aspirin-alone group and the aspirin+dipyrone group. Impaired pharmacodynamic response to aspirin occurred in 62% (14/21) of patients with aspirin and dipyrone co-medication. Only 10% (2/20) of aspirin treated patients without analgesic comedication displayed residual platelet reactivity (P=0.001; odds ratio [OR], 18 [95% CI, 3.2-100]). Excellent neurological recovery (measured by three months follow-up modified Rankin Scale<2) was observed in 80% (16/20) of patients in the aspirin-alone group and 48% (10/21) of patients in the aspirin+dipyrone group (P=0.037; OR, 4.4 [95% CI, 1.1-17.7]). CONCLUSIONS Dipyrone comedication in patients with stroke impairs pharmacodynamic response to aspirin. This is associated with worse clinical outcome. Therefore dipyrone should be used with caution in aspirin treated stroke patients. CLINICAL TRIAL REGISTRATION https://clinicaltrials.gov/show/NCT02148939; Identifier: NCT02148939.

Loss of Biglycan Enhances Thrombin Generation in Apolipoprotein E-Deficient Mice: Implications for Inflammation and Atherosclerosis.

Objective— Thrombin signaling promotes atherosclerosis by initiating inflammatory events indirectly through platelet activation and directly via protease-activated receptors. Therefore, endogenous thrombin inhibitors may be relevant modulators of atheroprogression and cardiovascular risk. In addition, endogenous thrombin inhibitors may affect the response to non–vitamin K-dependent oral anticoagulants. Here, the question was addressed whether the small leucine-rich proteoglycan biglycan acts as an endogenous thrombin inhibitor in atherosclerosis through activation of heparin cofactor II. Approach and Results— Biglycan concentrations were elevated in the plasma of patients with acute coronary syndrome and in male Apolipoprotein E -deficient ( ApoE −/−) mice. Biglycan was detected in the glycocalyx of capillaries and the subendothelial matrix of arterioles of ApoE −/− mice and in atherosclerotic plaques. Thereby a vascular compartment is provided that may mediate the endothelial and subendothelial activation of heparin cofactor II through biglycan. ApoE and Bgn double-deficient ( ApoE −/− /Bgn −/0) mice showed higher activity of circulating thrombin, increased platelet activation and platelet adhesion in vivo, supporting a role of biglycan in balancing thrombin activity. Furthermore, concentrations of circulating cytokines and aortic macrophage content were elevated in ApoE −/− /Bgn −/0 mice, suggesting a proinflammatory phenotype. Elevated platelet activation and macrophage accumulation were reversed by treating ApoE −/− /Bgn −/0 mice with the thrombin inhibitor argatroban. Ultimately, ApoE −/− /Bgn −/0 mice developed aggravated atherosclerosis. Conclusions— The present results indicate that biglycan plays a previously unappreciated protective role during the progression of atherosclerosis by inhibiting thrombin activity, platelet activation, and finally macrophage-mediated plaque inflammation. # Significance {#article-title-44}Objective—Thrombin signaling promotes atherosclerosis by initiating inflammatory events indirectly through platelet activation and directly via protease-activated receptors. Therefore, endogenous thrombin inhibitors may be relevant modulators of atheroprogression and cardiovascular risk. In addition, endogenous thrombin inhibitors may affect the response to non–vitamin K-dependent oral anticoagulants. Here, the question was addressed whether the small leucine-rich proteoglycan biglycan acts as an endogenous thrombin inhibitor in atherosclerosis through activation of heparin cofactor II. Approach and Results—Biglycan concentrations were elevated in the plasma of patients with acute coronary syndrome and in male Apolipoprotein E-deficient (ApoE−/−) mice. Biglycan was detected in the glycocalyx of capillaries and the subendothelial matrix of arterioles of ApoE−/− mice and in atherosclerotic plaques. Thereby a vascular compartment is provided that may mediate the endothelial and subendothelial activation of heparin cofactor II through biglycan. ApoE and Bgn double-deficient (ApoE−/−/Bgn−/0) mice showed higher activity of circulating thrombin, increased platelet activation and platelet adhesion in vivo, supporting a role of biglycan in balancing thrombin activity. Furthermore, concentrations of circulating cytokines and aortic macrophage content were elevated in ApoE−/−/Bgn−/0 mice, suggesting a proinflammatory phenotype. Elevated platelet activation and macrophage accumulation were reversed by treating ApoE−/−/Bgn−/0 mice with the thrombin inhibitor argatroban. Ultimately, ApoE−/−/Bgn−/0 mice developed aggravated atherosclerosis. Conclusions—The present results indicate that biglycan plays a previously unappreciated protective role during the progression of atherosclerosis by inhibiting thrombin activity, platelet activation, and finally macrophage-mediated plaque inflammation.

Analgesic medication with dipyrone in patients with coronary artery disease: Relation to MACCE

BACKGROUND The non-opioid analgesic dipyrone can trigger life-threatening blood formation disorders. However, it is frequently used, as many patients with coronary artery disease (CAD) rely on non-opioid analgesics to relieve pain. In this study, we investigated the incidence of death, myocardial infarction (MI) or stroke in CAD patients with aspirin and dipyrone comedication as compared to aspirin-alone. METHODS We conducted an observational pilot study in 72 CAD patients with aspirin ± dipyrone comedication in the department of cardiology of the University Hospital Düsseldorf. The primary end point was a composite of death, myocardial infarction (MI) or stroke. The secondary end points were the components of the primary end point. The median follow-up period was 3.2years. RESULTS The primary end point occurred 67% of patients in the aspirin+dipyrone group as compared to 31% in the aspirin-alone group (odds ratio [OR] 4.5, 95% confidence interval [CI] 1.7 to 12.3; P=0.0028;). All-cause mortality was significantly higher in the aspirin+dipyrone group (44%) than the aspirin-alone group (22%; OR 2.8, 95% CI 1.01 to 7.8; P=0.049). Ischemic events (MI and stroke) were more frequent in the aspirin+dipyrone group as compared to the aspirin alone group as well (OR 4, 95% CI 1.1 to 14; P=0.03). CONCLUSION In this hypothesis generating pilot analysis, dipyrone medication in aspirin treated coronary artery disease patients is associated with an increased cumulative incidence of death, MI or stroke as well as all-cause mortality and ischemic events. These data have to be confirmed in larger registries and trials. CLINICAL TRIAL REGISTRATION http://clinicaltrials.gov/ct2/show/NCT01402804; Identifier: NCT01402804; Date of registration: July 25, 2011.

Platelet reactivity in MitraClip patients

BACKGROUND Common complications during MitraClip procedure are bleeding and ischemic events. The right strategy of platelet inhibition is unknown and challenging, as there are substantial interindividual response-variabilities to antiplatelet drugs and additionally, many MitraClip patients are on permanent oral anticoagulation because of atrial fibrillation. We aimed to investigate the incidence of (i) high- and low on-treatment platelet reactivity (HTPR, LTPR) to antiplatelet medication and (ii) clinical complications in MitraClip patients. METHODS In an observational single-center cohort study we investigated 73 patients who underwent MitraClip implantation. Clopidogrel effects were measured using the vasodilator-stimulated protein phosphorylation (VASP) assay, aspirin effects by light-transmission aggregometry (LTA). Clinical complications were investigated during six-month follow-up. RESULTS HTPR to clopidogrel was observed in 44 patients, LTPR to clopidogrel in 6 patients. 16 patients had HTPR to aspirin. Major complications occurred in 12 patients, overall bleeding complications in 27 patients, overall ischemic events in two patients. The incidence of HTPR/LTPR did not differ between patients with- vs. without clinical complications. Bleeding complications were not more frequent in patients with additional oral anticoagulation. CONCLUSIONS In this study, the incidence of HTPR to clopidogrel was very high (60% of patients). Despite these insufficient clopidogrel antiplatelet effects, ischemic events were rare and bleeding complications more frequent. Additionally, many patients undergoing MitraClip procedure were on permanent oral anticoagulation because of atrial fibrillation. The optimal antithrombotic regiment should be investigated in large scale clinical trials under consideration of the high incidence of HTPR to clopidogrel medication in MitraClip patients.