Reference interval establishment and correlation research of urine thromboxane metabolites: Unveiling new possibilities in platelet activation.

BACKGROUND: Thromboxane metabolites could indirectly reflect platelet activation, among which 11-dehydro-thromboxane B2 (11dhTxB2) and 11-dehydro-2, 3-dinor thromboxane B2 (11dh23dinorTxB2) are two stable metabolites that are abundant in urine, and both are closely related to disease progression and drug use. However, most clinical application studies have focused on the single indicator of 11dhTxB2. We propose an LC-MS/MS method suitable for routine clinical screening with simultaneous determination of both metabolites and conduct preliminary studies in different populations. METHODS AND RESULTS: The thromboxane metabolites were extracted by liquid-liquid extraction and determined by LC-MS/MS. Reference intervals (RI) were established in 333 healthy adults and validated in 25 patients with coronary atherosclerosis (CA). This LC-MS/MS method was over a wide quantitative range (0.1-10 µmol/L), the imprecision and accuracy were 5.2 %-11 % and 89.3 %-106.5 %, and was suitable for clinical routine quantitative screening. The 95th percentile RI of unire 11dhTxB2 was 1220 (95 % CI: 1048, 1376) pg mg Cr -1, for 11dh23dinorTxB2, RI was 908 (95 % CI: 821, 1102) pg mg Cr -1. For the first time, we found a significant correlation between 11dhTxB2 and 11dh23dinorTxB2 in both healthy adults (r = 0.67, P < 0.001) and CA patients (r = 0.77, P < 0.001). CONCLUSION: The establishment of RI provides a reference for diseases related to platelet activation and the use of drugs, and the first discovery of the correlation between 11dhTxB2 and 11dh23dinorTxB2 in urine provides a new possibilitie for the diagnostic and prognostic of cardiovascular diseases.

Urinary 11-dehydrothromboxane B2 aspirin efficacy testing is sensitive to perioperative inflammation in pediatric solid-organ transplant patients.

BACKGROUND: Evidence for aspirin efficacy testing in pediatrics is limited, especially outside of cardiology, yet thrombotic events have high morbidity in other areas such as pediatric transplant surgery. Debates about whether thromboembolic events while on aspirin represent "aspirin resistance" or "high on-treatment platelet reactivity" persist, given the poor intertest agreement between testing platforms. PROCEDURE: This prospective observational study involved measuring aspirin efficacy using ex vivo testing of platelet aggregation (VerifyNow-Aspirin, VN) and urine 11-dehydrothromboxane B2 (AsprinWorks, UTxB2) contemporaneously at up to three time points after major noncardiac organ transplant surgery. The collection days (CD) were the second and seventh days after stable aspirin dosing and then a convalescent time point 2-9 months later. RESULTS: Fifty-five participants (age range, 0-21 years) were enrolled, having undergone total pancreatectomy with islet autotransplantation (N = 36), orthotopic liver transplantation (N = 18), and combined liver-kidney transplantation (N = 1). Platelet reactivity measured by VN remained unchanged, whereas UTxB2, which was elevated postoperatively, decreased significantly from CD1 to CD2 and CD3. Discordance in therapeutic efficacy was noted per manufacturer cutoffs, with therapeutic VN results in 86% of tests, whereas 12% of UTxB2 were therapeutic. Age-based stratification of UTxB2 results using previously published pediatric median levels increased overall UTxB2 therapeutic rates (80%) and intertest concordance (67% vs 27% if using adult range). No thrombotic events were observed. CONCLUSIONS: Our data suggest that urine thromboxane production may be an underappreciated reflection of postoperative inflammation. Validation of pediatric normal ranges for UTxB2 is a critical next step.

Pharmacodynamic effects of indobufen compared with aspirin in patients with coronary atherosclerosis.

PURPOSE: This study aimed to investigate the pharmacodynamic effects of indobufen and low-dose aspirin in patients with coronary atherosclerosis. METHODS: In the first phase, 218 patients with coronary atherosclerosis were randomly assigned to receive aspirin 100 mg once daily (standard dose); 100 mg once every 2 days; 100 mg once every 3 days; 50 mg twice daily; 75 mg once daily; 50 mg once daily; or indobufen 100 mg twice daily for 1 month. In the second phase, 20 healthy subjects were treated with indobufen 100 mg twice daily for 1 week followed after a 2-week washout by aspirin 100 mg once daily for 1 week. The primary outcome was arachidonic acid-induced platelet aggregation (PLAA), and the secondary outcomes included plasma thromboxane B2 (TXB2) and urinary 11-dehydro-TXB2 (11-dh-TXB2) levels at the end of each treatment.  RESULTS: In the first phase, compared with aspirin 100 mg once daily: all aspirin groups had similar suppression of PLAA whereas indobufen group had significantly less suppressed PLAA. Aspirin given every second or third day, and indobufen produced less suppression of plasma TXB2. All treatment regimens produced similar inhibition of 11-dh-TXB2. In the second phase, compared with aspirin, indobufen produced less suppression of plasma TXB2 at 8 h and 12 h after the last dose. CONCLUSIONS: Aspirin 50 mg twice daily, 75 mg once daily, and aspirin 50 mg once daily produce antiplatelet effects that are similar to aspirin 100 mg once daily. Aspirin given less often than once daily and indobufen 100 mg twice daily do not suppress platelets as effectively as aspirin 100 mg once daily.

Residual platelet reactivity in low-dose aspirin-treated patients with class 1 obesity.

BACKGROUND: Recent data suggest a decreased clinical efficacy of low-dose aspirin in patients weighing ≥70 kg. We therefore investigated the impact of body weight and class 1 obesity on thromboxane generation and platelet reactivity to arachidonic acid (AA) in 316 patients on dual antiplatelet therapy following angioplasty and stenting. METHODS: Platelet surface expression of P-selectin and activated glycoprotein (GP) IIb/IIIa in response to AA were determined by flow cytometry as sensitive markers of platelet activation. Urinary 11-dehydro-thromboxane B2 (11-dehydro-TXB2) and serum TXB2 were measured by commercially-available immunoassays. On-treatment residual AA-inducible platelet aggregation was assessed by light transmission aggregometry (LTA), the VerifyNow aspirin assay and multiple electrode aggregometry (MEA). RESULTS: Class 1 obesity was independently associated with increased platelet surface expression of P-selectin and activated GPIIb/IIIa, but not with urinary 11-dehydro-TXB2, serum TXB2, and on-treatment platelet aggregation by all assays. Of all measured parameters, only MEA showed a positive albeit very weak correlation with body weight (r = 0.13, p = 0.02). Furthermore, the results of all tests did not differ significantly between patients without and with a body weight ≥ 70 kg. After adjustment for age and diabetes by multivariate logistic regression analysis, the frequency of high-on treatment residual TXB2 generation and high on-treatment residual AA-inducible platelet reactivity (HRTG/HRPR) did not differ significantly between obese and non-obese patients. CONCLUSION: Class 1 obesity is associated with enhanced platelet activation in response to AA in patients on dual antiplatelet therapy. This seems to be independent of cyclooxygenase-1 inhibition and does not translate into HRTG/HRPR.

Increased platelet activity in tinnitus patients.

OBJECTIVE: The aim of our study was to establish whether or not tinnitus patients have higher platelet activity, as measured by plasma 11-dehydro-thromboxane B2 levels, compared with individuals without tinnitus. METHODS: The study group included patients without documented organic causes of tinnitus or a cause of non-vascular hearing impairment. Laboratory tests included complete blood count, biochemistry, coagulation activity, and thromboxane levels. To exclude a pathology in the cerebellopontine angle, CT and MRI were performed together with an X-ray scan of cervical vertebrae. For the purpose of this study, blood samples were screened for 11-dehydro-thromboxane B2 levels using commercial kits. RESULTS: A comparison of the main marker of increased platelet activity i.e., thromboxane levels of tinnitus patients with those of a control group, showed increased thromboxane levels in the former. The average plasma concentrations of 11-dehydro-thromboxane B2 were 2.0234±1.80 ng/ml in the group of tinnitus patients and 1.3247±1.33 ng/ml in the control group. Our results showed that patients with tinnitus have significantly higher values of 11-dehydro-thromboxane B2. CONCLUSION: Tinnitus patients showed higher levels of increased platelet activity, a marker that may play an important role in the pathogenesis of tinnitus.

Untargeted metabolomics reveals alterations in metabolites of lipid metabolism and immune pathways in the serum of rats after long-term oral administration of Amalaki rasayana.

Amalaki rasayana, a traditional preparation, is widely used by Ayurvedic physicians for the treatment of inflammatory conditions, cardiovascular diseases, and cancer. Metabolic alterations induced by Amalaki rasayana intervention are unknown. We investigated the modulations in serum metabolomic profiles in Wistar rats following long-term oral administration of Amalaki rasayana. Global metabolic profiling was performed of the serum of rats administered with either Amalaki rasayana (AR) or ghee + honey (GH) for 18 months and control animals which were left untreated. Amalaki rasayana components were confirmed from AR extract using HR-LCMS analysis. Significant reductions in prostaglandin J2, 11-dehydrothromboxane B2, and higher levels of reduced glutathione and glycitein metabolites were observed in the serum of AR administered rats compared to the control groups. Eleven different metabolites classified as phospholipids, glycerophospholipids, glucoside derivatives, organic acids, and glycosphingolipid were exclusively observed in the AR administered rats. Pathway analysis suggests that altered metabolites in AR administered rats are those associated with different biochemical pathways of arachidonic acid metabolism, fatty acid metabolism, leukotriene metabolism, G-protein mediated events, phospholipid metabolism, and the immune system. Targeted metabolomics confirmed the presence of gallic acid, ellagic acid, and arachidonic acid components in the AR extract. The known activities of these components can be correlated with the altered metabolic profile following long-term AR administration. AR also activates IGF1R-Akt-Foxo3 signaling axis in heart tissues of rats administered with AR. Our study identifies AR components that induce alterations in lipid metabolism and immune pathways in animals which consume AR for an extended period.

Transformation of Prostaglandin D2 to 11-Dehydro Thromboxane B2 by Baeyer-Villiger Oxidation.

Prostaglandin D2 is one of five chief prostanoids formed in the cyclooxygenase pathway of arachidonic acid oxidation. Except for a single oxygen atom, PGD2 is structurally identical to 11-dehydro thromboxane B2 (11d-TxB2 ), a urinary metabolite of the pro-aggregatory platelet activator, thromboxane A2 . The close structural relationship suggested that one might be transformed to the other. Accordingly, we tested whether the cyclopentanone of PGD2 can be expanded to the δ-lactone of 11d-TxB2 in a Baeyer-Villiger oxidation. Oxidation of PGD2 with two standard oxidants showed that 11d-TxB2 was formed only with H2 O2 but not with peracetic acid. Byproducts of the H2 O2 -mediated oxidation were hydroperoxide derivatives and isomers of PGD2 . Chemical oxidation of PGD2 to 11d-TxB2 may be a model for an equivalent enzymatic transformation, suggesting a possible link in the metabolism of PGD2 and thromboxane A2 .

Effects of reduced exposure to cigarette smoking on changes in biomarkers of potential harm in adult smokers: results of combined analysis of two clinical studies.

Purpose: Nonconventional vapor products (NVP), designed to reduce exposure to cigarette smoke toxicants (CSTs), could cause changes in biomarkers of potential harm (BoPH). Although, NVPs reduced CSTs exposure compared to conventional cigarettes (CC), the changes in the BoPH values varied among the studies. Hence, further information on BoPH using NVPs is needed. Material and methods: The data of two similarly designed studies using a kind of NVP, a noncombustion and nonheating inhaler type of smokeless tobacco product (NCIT) used under 31-day confinement, were pooled, and the differences in 15 BoPH between smokers and nonsmokers at baseline and between the 1 mg tar CC (CC1) group and NCIT group at Day 28/29 were analyzed. Results: At baseline, the levels of eight BoPH (red blood cells, white blood cells, 8-epi-prostaglandin F2α, 8-hydroxy-2'-deoxyguanosine, malondialdehyde, 11-dehydrothromboxane B2, total cholesterol and glucose) were significantly different between smokers and nonsmokers. At Day 28/29, the levels of six BoPH were significantly different between NCIT and CC1 (8-epi-prostaglandin F2α, malondialdehyde, 11-dehydrothromboxane B2: CC1 > NCIT, total bilirubin, low-density lipoprotein cholesterol and total cholesterol: CC1 < NCIT). Conclusions: Reduced exposure to CSTs has favorable effects on BoPH associated with oxidative stress, antioxidant capacity and platelet activation/coagulation but not in lipid metabolism.

Thromboxane-Dependent Platelet Activation in Obese Subjects with Prediabetes or Early Type 2 Diabetes: Effects of Liraglutide- or Lifestyle Changes-Induced Weight Loss.

Thromboxane (TX)-dependent platelet activation and lipid peroxidation, as reflected in vivo by the urinary excretion of 11-dehydro-TXB2 and 8-iso-prostaglandin (PG)F2α, play a key role in atherothrombosis in obesity and type 2 diabetes mellitus (T2DM) since the earlier stages. Thirty-five metformin-treated obese subjects with prediabetes or newly-diagnosed T2DM were randomized to the glucagon-like peptide receptor agonist (GLP-RA) liraglutide (1.8 mg/day) or lifestyle counseling until achieving a comparable weight loss (-7% of initial body weight), to assess whether changes in subcutaneous (SAT) and visceral (VAT) adipose tissue distribution (MRI), insulin sensitivity (Matsuda Index) and beta-cell performance (multiple sampling OGTT beta-index), with either intervention, might affect TX-dependent platelet activation, lipid peroxidation and inflammation. At baseline, Ln-8-iso-PGF2α (Beta = 0.31, p = 0.0088), glycosylated hemoglobin (HbA1c) (Beta = 2.64, p = 0.0011) Ln-TNF-α (Beta = 0.58, p = 0.0075) and SAT (Beta = 0.14, p = 0.044) were significant independent predictors of 11-dehydro-TXB2. After achievement of the weight loss target, a comparable reduction in U-11-dehydro-TXB2 (between-group p = 0.679) and 8-iso-PGF-2α (p = 0.985) was observed in both arms in parallel with a comparable improvement in glycemic control, insulin sensitivity, SAT, high-sensitivity C-reactive protein (hs-CRP). In obese patients with initial impairment of glucose metabolism, the extent of platelet activation is related to systemic inflammation, isoprostane formation and degree of glycemic control and abdominal SAT. Successful weight loss, achieved with either lifestyle changes or an incretin-based therapy, is associated with a significant reduction in lipid peroxidation and platelet activation.

Significance of urinary 11-dehydro-thromboxane B2 in age-related diseases: Focus on atherothrombosis.

Platelet activation plays a key role in atherogenesis and atherothrombosis. Biochemical evidence of increased platelet activation in vivo can be reliably obtained through non-invasive measurement of thromboxane metabolite (TXM) excretion. Persistent biosynthesis of TXA2 has been associated with several ageing-related diseases, including acute and chronic cardio-cerebrovascular diseases and cardiovascular risk factors, such as cigarette smoking, type 1 and type 2 diabetes mellitus, obesity, hypercholesterolemia, hyperhomocysteinemia, hypertension, chronic kidney disease, chronic inflammatory diseases. Given the systemic nature of TX excretion, involving predominantly platelet but also extraplatelet sources, urinary TXM may reflect either platelet cyclooxygenase-1 (COX-1)-dependent TX generation or COX-2-dependent biosynthesis by inflammatory cells and/or platelets, or a combination of the two, especially in clinical settings characterized by low-grade inflammation or enhanced platelet turnover. Although urinary 11-dehydro-TXB2 levels are largely suppressed with low-dose aspirin, incomplete TXM suppression by aspirin predicts the future risk of vascular events and death in high-risk patients and may identify individuals who might benefit from treatments that more effectively block in vivo TX production or activity. Several disease-modifying agents, including lifestyle intervention, antidiabetic drugs and antiplatelet agents besides aspirin have been shown to reduce TX biosynthesis. Taken together, these aspects may contribute to the development of promising mechanism-based therapeutic strategies to reduce the progression of atherothrombosis. We intended to critically review current knowledge on both the pathophysiological significance of urinary TXM excretion in clinical settings related to ageing and atherothrombosis, as well as its prognostic value as a biomarker of vascular events.

Immature platelets and antiplatelet therapy response to aspirin in Kawasaki disease.

INTRODUCTION: Kawasaki disease is a kind of systemic vasculitis that mainly damages moderate and small-sized blood vessels, and is a leading cause of coronary artery lesions (CAL). Antiplatelet therapy is a routine component of Kawasaki disease treatment strategies. So it is important to evaluate the antiplatelet effect of aspirin because of the individual biological variability of antiplatelet effect of aspirin. The immature platelet fraction (IPF) has attracted particular attention as it may influence the antiplatelet effect of aspirin. This study investigated the prognostic factors for evaluating the degree of vasculitis and the effect of antiplatelet therapy in children with Kawasaki disease. MATERIALS AND METHODS: Blood samples were collected from 44 patients with Kawasaki disease before aspirin treatment and 7 to 10 days after treatment. The IPF counts, percentage of the IPF, and highly fluorescent IPF were detected by a Sysmex XE-5000 instrument. The levels of 11-dehydrothromboxane B2 (11-DH-TXB2), soluble CD40 ligand (sCD40L), and soluble P-selectin (sP-selectin) were measured by ELISA. The correlation between the measured factors and the degree of coronary artery damage in Kawasaki disease was analyzed. RESULTS: We found that 11-DH-TXB2, sP-selectin, and sCD40L levels were much more elevated in the CAL group than in the non-coronary artery lesions (NCAL) group before aspirin treatment. The concentrations of 11-DH-TXB2, sCD40L, sP-selectin, and IPF were reduced after aspirin treatment in the NCAL group but not the CAL group. This is related to the degree of coronary artery damage in Kawasaki disease patients. Additionally, 11-DH-TXB2, sCD40L, sP-selectin, and IPF were positively correlated with the degree of coronary artery damage in Kawasaki disease patients. CONCLUSION: The current study suggests that the presence of high plasma concentrations of 11-DH-TXB2, sCD40L, sP-selectin, and IPF can be considered a risk factor and experimental biomarker for CAL in Kawasaki disease patients.

Effects of immunosuppressive agents on the hemostatic system in normal dogs.

BACKGROUND: In dogs, the effects of immunosuppressive medications on hemostasis are not well known. HYPOTHESIS/OBJECTIVES: The objective was to determine the effects of immunosuppressive medications on primary and secondary hemostasis. Our hypothesis was that cyclosporine and prednisone would increase markers of hypercoagulability and thromboxane synthesis, while azathioprine, mycophenolate mofetil, and leflunomide would have minimal effects on hemostasis. ANIMALS: Eight healthy dogs. METHODS: A randomized, cross-over study used aggregometry, the PFA-100 platelet function analyzer, viscoelastometry, platelet count, and prothrombin and activated partial thromboplastin times to evaluate hemostasis during the administration of prednisone, azathioprine, cyclosporine, mycophenolate mofetil, and leflunomide for 1 week each at standard oral doses. Urine 11-dehydro-thromboxane-B2 (11-dTXB2 ) and 6-keto-prostaglandin-F1α (6-keto-PGF1α ) concentrations, normalized to urine creatinine concentration, were measured. RESULTS: The aggregometry amplitude decreased from 51 ± 21 to 27 ± 14 (P = .002) during leflunomide treatment (ADP activation), but there were no differences in amplitude (P = .240) for any medications when platelets were activated with collagen. For all medications, there were no significant differences in viscoelastometry indices (ACT, P = .666; ClotRate, P = .340; and platelet function, P = .411) and platelet count (P = .552). Compared with pretreatment values, urinary 11-dTXB2 -to-creatinine ratio increased (P = .001) after drug administration (from 3.7 ± 0.6 to 5.6 ± 1.1). Cyclosporine was associated with an increase (P < .001) in the 6-keto-PGF1α -to-creatinine ratio (from 10.3 ± 4.6 to 22.1 ± 5.3). CONCLUSIONS AND CLINICAL IMPORTANCE: Most immunosuppressive drugs do not enhance platelet function or coagulation in healthy dogs, suggesting that these medications might not predispose hypercoagulable dogs to thromboembolism. The results of our study need to be correlated with the clinical outcomes of hypercoagulable dogs.

Reduced Variability to Aspirin Antiplatelet Effect by the Coadministration of Statins in High-Risk Patients for Cardiovascular Disease.

We studied the influence of cardiovascular (CV) risk factors, previous CV events, and cotreatments with preventive medicines, on residual platelet thromboxane (TX)B2 production in 182 patients chronically treated with enteric coated (EC)-aspirin (100 mg/day). The response to aspirin was also verified by assessing arachidonic acid-induced platelet aggregation and urinary 11-dehydro-TXB2 levels. Residual serum TXB2 levels exceeded the upper limit value for an adequate aspirin response in 14% of individuals. This phenomenon was detected at 12 hours after dosing with aspirin. The coadministration of statins (mostly atorvastatin) was an independent predictor of residual serum TXB2 levels, and the percentage of patients with enhanced values was significantly lower in statin users vs. nonusers. We provide evidence in vitro that atorvastatin reduced residual TXB2 generation by increasing the extent of acetylation of platelet COX-1 by aspirin. In conclusion, the coadministration of statins may counter the mechanisms associated with reduced bioavailability of aspirin detected in some individuals with CV disease.

Glucocorticoids impair platelet thromboxane biosynthesis in community-acquired pneumonia.

Previous reports suggest that community-acquired pneumonia (CAP) is associated with an enhanced risk of myocardial infarction (MI) and that enhanced platelet activation may play a role. Aims of this study were to investigate if urinary excretion of 11-dehydro-thromboxane (Tx) B2, a reliable marker of platelet activation in vivo, was elevated in CAP and whether glucocorticoid administration reduced platelet activation. Three-hundred patients hospitalized for CAP were recruited and followed-up until discharge. Within the first 2 days from admission, urinary 11-dehydro-TxB2 and serum levels of methylprednisolone and betamethasone were measured. 11-Dehydro-TxB2 was also measured in a control group of 150 outpatients, matched for age, sex, and comorbidities. Finally, in-vitro studies were performed to assess if glucocorticoids affected platelet activation, at the same range of concentration found in the peripheral circulation of CAP patients treated with glucocorticoids. Compared to controls, CAP patients showed significantly higher levels of 11-dehydro-TxB2 (110 [69-151] vs. 163 [130-225] pg/mg creatinine; p < 0.001). During the in-hospital stay, 31 patients experienced MI (10%). A COX regression analysis showed that 11-dehydro-TxB2 independently predicted MI (p = .005). CAP patients treated with glucocorticoids showed significantly lower levels of 11-dehydro-TxB2 compared to untreated ones (147 [120-201] vs. 176 [143-250] pg/mg creatinine; p < 0.001). In vitro, glucocorticoids-treated platelets showed a dose-dependent decrease of ADP-induced platelet aggregation, TxB2 production, cPLA2 phosphorylation and arachidonic acid release from the platelet membrane. In conclusion, platelet TxB2 is overproduced in CAP patients and may be implicated in MI occurrence. Glucocorticoids reduce platelet release of TxB2 in vitro and urinary excretion of 11-dehydro-TxB2 in vivo and may be a novel tool to decrease platelet activation in this setting.

Kidney Transplantation in a Patient Lacking Cytosolic Phospholipase A2 Proves Renal Origins of Urinary PGI-M and TX-M.

RATIONALE: The balance between vascular prostacyclin, which is antithrombotic, and platelet thromboxane A2, which is prothrombotic, is fundamental to cardiovascular health. Prostacyclin and thromboxane A2 are formed after the concerted actions of cPLA2α (cytosolic phospholipase A2) and COX (cyclooxygenase). Urinary 2,3-dinor-6-keto-PGF1α (PGI-M) and 11-dehydro-TXB2 (TX-M) have been taken as biomarkers of prostacyclin and thromboxane A2 formation within the circulation and used to explain COX biology and patient phenotypes, despite concerns that urinary PGI-M and TX-M originate in the kidney. OBJECTIVE: We report data from a remarkable patient carrying an extremely rare genetic mutation in cPLA2α, causing almost complete loss of prostacyclin and thromboxane A2, who was transplanted with a normal kidney resulting in an experimental scenario of whole-body cPLA2α knockout, kidney-specific knockin. By studying this patient, we can determine definitively the contribution of the kidney to the productions of PGI-M and TX-M and test their validity as markers of prostacyclin and thromboxane A2 in the circulation. METHODS AND RESULTS: Metabolites were measured using liquid chromatography-tandem mass spectrometry. Endothelial cells were grown from blood progenitors. Before kidney transplantation, the patient's endothelial cells and platelets released negligible levels of prostacyclin (measured as 6-keto-prostaglandin F1α) and thromboxane A2 (measured as TXB2), respectively. Likewise, the urinary levels of PGI-M and TX-M were very low. After transplantation and the establishment of normal renal function, the levels of PGI-M and TX-M in the patient's urine rose to within normal ranges, whereas endothelial production of prostacyclin and platelet production of thromboxane A2 remained negligible. CONCLUSIONS: These data show that PGI-M and TX-M can be derived exclusively from the kidney without contribution from prostacyclin made by endothelial cells or thromboxane A2 by platelets in the general circulation. Previous work relying on urinary metabolites of prostacyclin and thromboxane A2 as markers of whole-body endothelial and platelet function now requires reevaluation.

Urinary 11-dehydro-thromboxane B2 levels are associated with vascular inflammation and prognosis in atherosclerotic cardiovascular disease.

Cyclooxygenase-derived thromboxane (TxA2) and prostacyclin (PGI2) regulate atherogenesis in preclinical models. However, the relationship between TxA2 and PGI2 biosynthesis, vascular inflammation, and atherosclerotic cardiovascular disease (ASCVD) progression in humans remains unclear. The association between stable urine metabolites of thromboxane (TxA2-M) and prostacyclin (PGI2-M), circulating levels of cellular adhesion molecules (CAMs: E-selectin, P-selectin), chemokines and C-reactive protein, and the incidence of major adverse cardiovascular events (MACE) were evaluated in 120 patients with stable ASCVD on aspirin therapy. Urinary TxA2-M levels were significantly correlated with circulating P-selectin (r=0.319, p<0.001) and E-selectin (r=0.245, p=0.007) levels, and associated with higher risk of MACE (p=0.043). In contrast, PGI2-M levels were not significantly associated with CAM levels or MACE. These results provide insight into the contribution of TxA2 biosynthesis to ASCVD progression in humans, and suggest that patients with elevated TxA2-M levels may be predisposed to advanced platelet and endothelial activation and higher risk of adverse cardiovascular outcomes.

Prognostic value of urinary 11-dehydro-thromboxane B2 for mortality: A cohort study of stable coronary artery disease patients treated with aspirin.

AIM: There is a variable cardiovascular risk reduction attributable to aspirin because of individual differences in the suppression of thromboxane A2 and its downstream metabolite 11-dehydro-thromboxane B2 (11dhTxB2 ). The aim of this study is to evaluate the optimal cut point of urinary 11dhTxB2 for the risk of mortality in aspirin-treated coronary artery disease (CAD) patients. METHODS AND RESULTS: This was a prospective cohort study including stable CAD patients who visited the Baylor Heart and Vascular Hospital in Dallas or the Texas Heart Hospital Baylor Plano, TX between 2010 and 2013. The outcome of all-cause mortality was ascertained from chart review and automated sources. The 449 patients included in this analysis had a mean age of 66.1 ± 10.1 years. 67 (14.9%) patients died within 5 years; 56 (87.5%) of the 64 patients with known cause of death suffered a cardiovascular related mortality. Baseline ln(urinary 11dhTxB2 /creatinine) ranged between 5.8 and 11.1 (median = 7.2) with the higher concentrations among those who died (median: 7.6) than those who survived (median = 7.2, P < 0.001). Using baseline ln(11dhTxB2 ) to predict all-cause mortality, the area under the curve was 0.70 (95% CI: 0.64-0.76). The optimal cut point was found to be ln(7.38) = 1597.8 pg/mg, which had the following decision statistics: sensitivity = 0.67, specificity = 0.62, positive predictive value = 0.24, negative predictive value = 0.92, and accuracy = 0.63. CONCLUSION: Our data indicate the optimal cut point for urine 11dhTxB2 is 1597.8 (pg/mg) for the risk prediction of mortality over five years in stable patients with CAD patients treated with aspirin.

Effects of aspirin dose escalation on platelet function and urinary thromboxane and prostacyclin levels in normal dogs.

Established "low" aspirin dosages inconsistently inhibit platelet function in dogs. Higher aspirin dosages consistently inhibit platelet function, but are associated with adverse effects. The objectives of this study were to use an escalation in dosage to determine the lowest aspirin dosage that consistently inhibited platelet function without inhibiting prostacyclin synthesis. Eight dogs were treated with five aspirin dosages: 0.5 mg/kg q24h, 1 mg/kg q24h, 2 mg/kg q24h, 4 mg/kg q24h and 10 mg/kg q12h for 7 days. Utilizing aggregometry and a whole-blood platelet function analyzer (PFA-100), platelet function was evaluated before and after treatment. Urine 11-dehydro-thromboxane-B2 (11-dTXB2 ) and 6-keto-prostaglandin-F1α (6-keto-PGF1α ), were measured. Compared to pretreatment, there were significant post-treatment decreases in the maximum aggregometry amplitude and increases in the PFA-100 closure times for all dosages expect 0.5 mg/kg q24h. There was no difference in amplitude or closure time among the 2 mg/kg q24h, 4 mg/kg q24h, and 10 mg/kg q12h dosages. Compared to pretreatment values, there was a significant decrease in urinary 11-dTXB2 -to-creatinine and 6-keto-PGF1α -to-creatinine ratios, but there was no dose-dependent decrease for either metabolite. An aspirin dosage of 2 mg/kg q24h consistently inhibits platelet function without decreasing prostacyclin synthesis significantly more than lower aspirin dosages.

Genetic variants in PPARGC1B and CNTN4 are associated with thromboxane A2 formation and with cardiovascular event free survival in the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT).

BACKGROUND AND AIMS: Elevated urinary 11-dehydro thromboxane B2 (TxB2), a measure of thromboxane A2 formation in vivo, predicts future atherothrombotic events. To further understand this relationship, the genetic determinants of 11-dehydro TxB2 and their associations with cardiovascular morbidity were investigated in this study. METHODS: Genome-wide and targeted genetic association studies of urinary 11-dehydro TxB2 were conducted in 806 Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) participants. RESULTS: The strongest associations were in PPARGC1B (rs4235745, rs32582, rs10515638) and CNTN4 (rs10510230, rs4684343), these 5 single nucleotide polymorphisms (SNPs) were independently associated with 11-dehydro TxB2 formation. Haplotypes of 11-dehydro TxB2 increasing alleles for both PPARGC1B and CNTN4 were significantly associated with 11-dehydro TxB2, explaining 5.2% and 4.5% of the variation in the whole cohort, and 8.8% and 7.9% in participants not taking aspirin, respectively. In a second ASCOT population (n = 6199), addition of these 5 SNPs significantly improved the covariate-only Cox proportional hazards model for cardiovascular events (chisq = 14.7, p=0.01). Two of the risk alleles associated with increased urinary 11-dehydro TxB2 were individually associated with greater incidences of cardiovascular events - rs10515638 (HR = 1.31, p=0.01) and rs10510230 (HR = 1.25, p=0.007); effect sizes were larger in those not taking aspirin. CONCLUSIONS: PPARGC1B and CNTN4 genotypes are associated with elevated thromboxane A2 formation and with an excess of cardiovascular events. Aspirin appears to blunt these associations. If specific protection of PPARGC1B and CNTN4 variant carriers by aspirin is confirmed by additional studies, PPARGC1B and CNTN4 genotyping could potentially assist in clinical decision making regarding the use of aspirin in primary prevention.

Differential Impact of Serial Measurement of Nonplatelet Thromboxane Generation on Long-Term Outcome After Cardiac Surgery.

BACKGROUND: Systemic thromboxane generation, not suppressible by standard aspirin therapy and likely arising from nonplatelet sources, increases the risk of atherothrombosis and death in patients with cardiovascular disease. In the RIGOR (Reduction in Graft Occlusion Rates) study, greater nonplatelet thromboxane generation occurred early compared with late after coronary artery bypass graft surgery, although only the latter correlated with graft failure. We hypothesize that a similar differential association exists between nonplatelet thromboxane generation and long-term clinical outcome. METHODS AND RESULTS: Five-year outcome data were analyzed for 290 RIGOR subjects taking aspirin with suppressed platelet thromboxane generation. Multivariable modeling was performed to define the relative predictive value of the urine thromboxane metabolite, 11-dehydrothromboxane B2 (11-dhTXB2), measured 3 days versus 6 months after surgery on the composite end point of death, myocardial infarction, revascularization or stroke, and death alone. 11-dhTXB2 measured 3 days after surgery did not independently predict outcome, whereas 11-dhTXB2 >450 pg/mg creatinine measured 6 months after surgery predicted the composite end point (adjusted hazard ratio, 1.79; P=0.02) and death (adjusted hazard ratio, 2.90; P=0.01) at 5 years compared with lower values. Additional modeling revealed 11-dhTXB2 measured early after surgery associated with several markers of inflammation, in contrast to 11-dhTXB2 measured 6 months later, which highly associated with oxidative stress. CONCLUSIONS: Long-term nonplatelet thromboxane generation after coronary artery bypass graft surgery is a novel risk factor for 5-year adverse outcome, including death. In contrast, nonplatelet thromboxane generation in the early postoperative period appears to be driven predominantly by inflammation and did not independently predict long-term clinical outcome.