Elisabetta Ferrante

The recovery of platelet cyclooxygenase activity explains interindividual variability in responsiveness to low-dose aspirin in patients with and without diabetes

See also Lordkipanidze M, Harrison P. Aspirin twice a day keeps new COX‐1 at bay. This issue, pp 1217–9.

The contribution of cyclooxygenase-1 and -2 to persistent thromboxane biosynthesis in aspirin-treated essential thrombocythemia: implications for antiplatelet therapy

We tested whether cyclooxygenase 2 (COX-2) expression and unacetylated COX-1 in newly formed platelets might contribute to persistent thromboxane (TX) biosynthesis in aspirin-treated essential thrombocythemia (ET). Forty-one patients on chronic aspirin (100 mg/day) and 24 healthy subjects were studied. Platelet COX-2 expression was significantly increased in patients and correlated with thiazole orange-positive platelets (r = 0.71, P < .001). The rate of TXA(2) biosynthesis in vivo, as reflected by urinary 11-dehydro-TXB(2) (TXM) excretion, and the maximal biosynthetic capacity of platelets, as reflected by serum TXB(2), were higher in patients compared with aspirin-treated healthy volunteers. Serum TXB(2) was significantly reduced by the selective COX-2 inhibitor NS-398 added in vitro. Patients were randomized to adding the selective COX-2 inhibitor, etoricoxib, or continuing aspirin for 7 days. Etoricoxib significantly reduced by approximately 25% TXM excretion and serum TXB(2). Fourteen of the 41 patients were studied again 21 (+/- 7) months after the first visit. Serum TXB(2) was consistently reduced by approximately 30% by adding NS398 in vitro, while it was completely suppressed with 50 microM aspirin. Accelerated platelet regeneration in most aspirin-treated ET patients may explain aspirin-persistent TXA(2) biosynthesis through enhanced COX-2 activity and faster renewal of unacetylated COX-1. These findings may help in reassessing the optimal antiplatelet strategy in ET.

Impact of Escalating Loading Dose Regimens of Ticagrelor in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention: Results of a Prospective Randomized Pharmacokinetic and Pharmacodynamic Investigation.

OBJECTIVES The goal of this study was to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of escalating ticagrelor loading dose (LD) regimens in primary percutaneous coronary intervention (PPCI). BACKGROUND Patients with ST-segment elevation myocardial infarction undergoing PPCI frequently have suboptimal platelet inhibition in the early hours after ticagrelor LD. The use of high ticagrelor LD regimens has been hypothesized to optimize platelet inhibition in PPCI. METHODS This was a prospective, randomized study of escalating ticagrelor LD regimens (180 mg, 270 mg, or 360 mg) in PPCI (N = 52). PK/PD analyses were performed before and 30 min, 1, 2, 4, 8, and 24 h post-LD. PK assessments included exposure to ticagrelor and its metabolite (AR-C124910XX). PD assessments included P2Y12 reaction units (PRU) measured by VerifyNow P2Y12 and platelet reactivity index (PRI) measured by vasodilator-stimulated phosphoprotein (VASP). RESULTS Platelet reactivity was elevated during the first 2 h post-LD. There were no differences in PRU between groups during the study time course (p = 0.179). There were no significant differences in PRU levels across groups at all time points, except at 1 h (p = 0.017) where platelet reactivity was lowest with a 270-mg LD. No differences were found between the 180-mg and 360-mg groups (primary endpoint; p > 0.999). High on-treatment platelet reactivity rates were not different across groups, except at 1 hour (p = 0.038). Parallel PD findings were observed with VASP-PRI. PK analysis showed a delay in ticagrelor absorption and generation of AR-C124910XX, irrespective of dose. Although morphine was associated with a delay in ticagrelor PK/PD, it was not an independent predictor of high on-treatment platelet reactivity. CONCLUSIONS ST-segment elevation myocardial infarction patients undergoing PPCI frequently exhibit impaired response to ticagrelor in the early hours after drug administration, which cannot be overcome by increasing LD regimens. These PD findings are largely attributed to an impaired PK profile, indicating a delay in drug absorption compared with that reported in stable clinical settings. (High Ticagrelor Loading Dose in STEMI; NCT01898442).

A head-to-head pharmacodynamic comparison of prasugrel vs. ticagrelor after switching from clopidogrel in patients with coronary artery disease: results of a prospective randomized study

AIMS Pharmacodynamic (PD) studies comparing prasugrel and ticagrelor have reached inconsistent findings. Therefore, a comprehensive investigation comparing the PD effects of prasugrel vs. ticagrelor after switching from clopidogrel therapy, exploring both loading dose (LD) and maintenance dose (MD) regimens represented the aim of this study. METHODS AND RESULTS Patients (n = 110) with coronary artery disease were randomized to prasugrel (60 mg LD/10 mg MD q.d.) or ticagrelor (180 mg LD/90 mg MD b.i.d) therapy for 1 week. Pharmacodynamic assessments were conducted using three assays (vasodilator-stimulated phosphoprotein, VerifyNow P2Y12, and light transmittance aggregometry, LTA) at baseline, 30 min, 2, 24 h, and 1 week. The impact of initiating ticagrelor MD 12 vs. 24 h after LD administration was also assessed. Switching clopidogrel-treated patients to an LD of prasugrel or ticagrelor was associated with a reduction in platelet reactivity at 30 min and was sustained at all time points up to 1 week with the MD (P < 0.001 for all assays). Platelet reactivity was similar with prasugrel and ticagrelor with all assays at 30 min, 2 h, and 1 week (P > 0.05 for all time points), with the exception of LTA at 30 min (lower with prasugrel; P = 0.003). At 24 h, platelet reactivity was lower among patients initiating ticagrelor MD after 12 vs. 24 h post-LD. Rates of high platelet reactivity (HPR) were markedly reduced and similar between groups. CONCLUSION Prasugrel and ticagrelor exert similar levels of P2Y12 inhibition achieving more potent PD effects and reduced HPR rates compared with clopidogrel which are reached promptly following LD and sustained with MD. CLINICALTRIALSGOV IDENTIFIER NCT01852175.

Endogenous Secretory RAGE in Obese Women: Association with Platelet Activation and Oxidative Stress

CONTEXT The receptor for advanced glycation end-products (RAGE) has been implicated in obesity-related metabolic disease and accelerated atherothrombosis. OBJECTIVE We tested the hypothesis that changes in endogenous secretory (es)RAGE levels as a result of excess adiposity and oxidative stress may contribute to enhancing platelet activation in obese women, thus increasing the cardiovascular risk. PATIENTS Eighty otherwise healthy obese women and 20 nonobese women were studied. RESULTS esRAGE and plasma adiponectin were reduced in obese women [median (interquartile range), 0.18 (0.13-0.26) vs. 0.38 (0.20-0.48) ng/ml, P = 0.003; and 4.4 (2.8-6.4) vs. 10.0 (6.9-12.5) μg/ml, P < 0.0001, respectively] who also displayed higher urinary 11-dehydro-thromboxane B(2) (11-dehydro-TXB(2)) [795 (572-1089) vs. 211 (135-301) pg/mg creatinine; P < 0.0001] and 8-iso-prostaglandin F(2α) (8-iso-PGF(2α)) [544 (402-698) vs. 149 (98-219) pg/mg creatinine; P < 0.0001] compared to nonobese women. Direct correlations between plasma adiponectin and esRAGE (Rho = 0.43; P < 0.0001) and between urinary 8-iso-PGF(2α) and 11-dehydro-TXB(2) (Rho = 0.36; P = 0.001) were observed in obese women. Moreover, plasma esRAGE and urinary 11-dehdro-TXB(2) were inversely related (Rho = -0.29; P = 0.008). On multiple linear regression analysis, urinary 8-iso-PGF(2α) and plasma esRAGE were independent predictors of urinary 11-dehydro-TXB(2). In five obese women, a short-term weight loss program gave a significant increase in esRAGE and decrease in urinary 8-iso-PGF(2α) and 11-dehydro-TXB(2). CONCLUSION In otherwise healthy obese women, low plasma esRAGE levels are associated with reduced circulating adiponectin and enhanced thromboxane biosynthesis, which is in part mediated by increased lipid peroxidation. Thus, excess adiposity may be implicated in RAGE hyperactivation and thromboxane-dependent platelet activation, contributing to obesity-related metabolic and vascular disease.

Platelet function testing in contemporary clinical and interventional practice.

Opinion statementDual antiplatelet therapy with a combination of aspirin and an inhibitor of the ADP P2Y12 receptor is the recommended treatment for patients with acute coronary syndrome or who are undergoing percutaneous coronary intervention (PCI). However, patients may continue to have ischemic recurrences, including stent thrombosis, which have been linked with the well-known variability in individual response to antiplatelet therapy, and clopidogrel in particular. There are currently several assays available to measure platelet reactivity, and platelet function testing has been shown to be a valuable tool to assess the pharmacodynamic efficacy of antiplatelet drugs. Moreover, platelet reactivity has important prognostic implications, as several studies have shown an association with thrombotic and bleeding events in patients with high and low platelet reactivity, respectively. Consequently, over the past years there has been a plethora of studies investigating the optimal range of platelet reactivity associated with the highest protection against ischemic complications and the lowest risk of bleeding. Given the correlation between on-treatment platelet reactivity and outcomes, the use of platelet function testing has also been advocated to create personalized antiplatelet therapy. Several studies have been conducted in this field, but major clinical trials have failed to demonstrate a benefit of such a strategy in improving clinical outcomes. Indeed, inherent limitations of these trials may have contributed to their failure. The present manuscript provides an overview on the role of platelet function testing in contemporary clinical and interventional practice.

Determinants of thromboxane biosynthesis in rheumatoid arthritis: Role of RAGE and oxidant stress

Thromboxane (TX) biosynthesis by platelets and other cells in response to inflammatory triggers may provide a link between chronic inflammatory disease and atherothrombosis in rheumatoid arthritis (RA). In this study, we investigated the determinants of TX biosynthesis in RA, with particular reference to enhanced oxidative stress, receptor for advanced glycation end-products (RAGE) hyperactivity, and anti-tumor necrosis factor (TNF) treatment. Fifty-four patients with RA and 20 healthy subjects were recruited and a cross-sectional comparison of urinary 11-dehydro-TXB(2), 8-iso-PGF(2alpha), and plasma endogenous secretory RAGE (esRAGE) levels was performed between patients and controls. Urinary 11-dehydro-TXB(2) was significantly higher in RA patients than in healthy controls [425 (309-592) vs 233 (158-327) pg/mg creatinine, P<0.0001]. Furthermore, urinary 8-iso-PGF(2alpha) [323 (221-515) vs 172 (91-292) pg/mg creatinine, P<0.0001] and plasma esRAGE [155 (100-240) vs 377 (195-486) pg/ml, P=0.001] were higher and lower, respectively, in patients than in controls. A direct correlation was found between urinary 11-dehydro-TXB(2) and 8-iso-PGF(2alpha) only in patients not on anti-TNF therapy (r=0.420, P=0.021). Conversely, patients on anti-TNF therapy showed significantly lower urinary 8-iso-PGF(2alpha) [284 (201-373) vs 404 (241-539) pg/mg creatinine, P=0.043] but not 11-dehydro-TXB(2) than anti-TNF-treated subjects, with esRAGE as the only independent predictor of 11-dehydro-TXB(2) in this group of patients (adjusted R(2)=0.496, beta=-0.725, SEM=0.025, P=0.001). In conclusion, we provide biochemical evidence of enhanced TX biosynthesis in patients with RA, driven, at least in part, by lipid peroxidation. Treatment with anti-TNF agents may blunt isoprostane generation in the absence of significant effects on TX biosynthesis. We suggest that RAGE hyperactivity may escape TNF blockade, thus contributing to persistent TX biosynthesis in this setting.

Inflammation, oxidative stress and platelet activation in aspirin-treated critical limb ischaemia: Beneficial effects of iloprost

Platelets critically contribute to atherothrombosis and worsening ischaemia in patients with peripheral arterial disease (PAD), eventually leading to critical limb ischaemia (CLI). Furthermore, persistent platelet activation despite antiplatelet therapy has been reported in this setting. The prostacyclin analogue iloprost is currently recommended in CLI patients for its effects in relieving symptoms by promoting local perfusion. In this study, we investigated the effects of iloprost infusion on urinary 11-dehydro-TXB₂ and 8-iso-PGF(₂α) excretion rate, as in vivo indexes of thromboxane-dependent platelet activation and lipid peroxidation, respectively, and on platelet-derived proinflammatory sCD40L and nitric oxide bioavailability in 44 patients with CLI while on chronic treatment with low-dose aspirin. Daily iloprost infusion for one-week significantly decreased urinary 11-dehydro-TXB₂ [499 (277-807) vs. 380 (189-560) pg/mg creatinine, p < 0.0001] and 8-iso-PGF(₂α) [533 (316-842) vs. 334 (196-540) pg/mg creatinine, p < 0.0001] as well as plasma sCD40L [1540 (1005-3015) vs. 948 (845-2030) pg/ml, p < 0.0001]. Furthermore, a significant increase in plasma nitrate plus nitrite levels has been observed [26.8 (18.8-35.9) vs. 43.7 (33.0-75.5) μM, p < 0.0001]. A significant direct correlation was also found between urinary 8-iso-PGF(₂α) and 11-dehydro-TXB2 before and after iloprost treatment (Rho = 0.695, p < 0.0001). In conclusion, we report that a short-term course of iloprost is able to significantly reduce residual thromboxane biosynthesis, oxidative stress, endothelial dysfunction and platelet-derived inflammation in low-dose aspirin treated patients with CLI.

Unmet needs in the management of acute myocardial infarction: role of novel protease-activated receptor-1 antagonist vorapaxar

Platelet activation with subsequent aggregation is a complex process leading to thrombus formation, which remains a key component for atherothrombotic manifestations, in particular myocardial infarction. Therefore, antiplatelet therapies are pivotal for the treatment of these patients. Current oral antiplatelet therapies used for secondary prevention of ischemic recurrences include aspirin and adenosine diphosphate P2Y12 platelet-receptor antagonists. However, despite these therapies, patients who have experienced a myocardial infarction remain at risk for ischemic recurrences. Therefore, more aggressive secondary prevention measures have been an area of research, including identifying additional targets modulating platelet-activation and -aggregation processes. Among these, thrombin-mediated platelet activation via protease-activated receptors (PARs) has been subject to extensive clinical investigation. Several PAR-1 receptor antagonists have been developed. However, vorapaxar is the only one that has completed large-scale clinical investigation. The present manuscript will provide an overview on the role of thrombin-mediated signaling, the impact of PAR-1 blockade with vorapaxar on ischemic and bleeding outcomes, and the potential role for vorapaxar in clinical practice.

Pharmacodynamic Effects of Ticagrelor Dosing Regimens in Patients on Maintenance Ticagrelor Therapy : Results From a Prospective, Randomized, Double-Blind Investigation

OBJECTIVES The aim of this study was to assess the impact of ticagrelor dosing regimens on pharmacodynamic (PD) profiles in patients on maintenance ticagrelor therapy. BACKGROUND Many patients on maintenance P2Y12-inhibiting therapies may require coronary revascularization procedures, raising a common clinical question with regard to the dosing regimen of the P2Y12-inhibiting agent to be used. To date, investigations assessing dosing regimens of P2Y12 receptor inhibitors in patients on maintenance therapy have been only assessed with thienopyridines, but not with ticagrelor. METHODS This was a prospective, randomized, double-blind, placebo-controlled study assessing the PD effects of 2 dosing regimens of ticagrelor in patients on standard aspirin and ticagrelor maintenance therapy. A total of 60 patients were randomized to either 90 mg (maintenance dose [MD] group) or 180 mg (loading dose [LD] group) dose of ticagrelor. PD assessments were conducted at 3 time points (baseline, 1 h and 4 h). PD assessments were defined according to the platelet reactivity index (PRI) (vasodilator-stimulated phosphoprotein phosphorylation assay), P2Y12 reaction unit (VerifyNow P2Y12 assay) and adenosine diphosphate-induced platelet aggregation by light transmittance aggregometry. RESULTS There were no differences in baseline levels of platelet reactivity with all assays. Intergroup comparisons by means of repeated-measures analysis adjusted for baseline PRI values showed that the LD group had significantly lower PRI levels compared with the MD group during the overall study time course (p = 0.031). Consistent findings were found for P2Y12 reaction unit (p = 0.026) and light transmittance aggregometry (p = 0.004). Intragroup comparisons showed that a more prompt and sustained platelet inhibitory effect was achieved more consistently with an LD regimen compared with a MD regimen. CONCLUSIONS In patients on maintenance ticagrelor therapy, a 180-mg LD regimen of ticagrelor is associated with more potent and prompt platelet inhibition compared with a 90-mg MD. (Impact of Ticagrelor Re-Load Pharmacodynamic Profiles; NCT01731041).