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PurposeThis study aimed to investigate the pharmacodynamic effects of indobufen and low-dose aspirin in patients with coronary atherosclerosis.MethodsIn 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. ResultsIn 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.ConclusionsAspirin 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.

Low‐dose aspirin is currently recommended for patients with polycythemia vera (PV), a myeloproliferative neoplasm with increased risk of arterial and venous thromboses. Based on aspirin pharmacodynamics in essential thrombocythemia, a twice‐daily regimen is recommended for patients with PV deemed at particularly high thrombotic risk. We investigated the effects of low‐dose aspirin on platelet cyclooxygenase activity and in vivo platelet activation in 49 patients with PV, as assessed by serum thromboxane (TX) B2 and urinary TXA2/TXB2 metabolite (TXM) measurements, respectively. A previously described pharmacokinetic‐pharmacodynamic in silico model was used to simulate the degree of platelet TXA2 inhibition by once‐daily (q.d.) and twice‐daily (b.i.d.) aspirin, and to predict the effect of missing an aspirin dose during q.d. and b.i.d. regimens. Serum TXB2 averaged 8.2 (1.6–54.7) ng/ml and significantly correlated with the platelet count (γ = 0.39) and urinary TXM (γ = 0.52) in multivariable analysis. One‐third of aspirin‐treated patients with PV displayed less‐than‐maximal platelet TXB2 inhibition, and were characterized by significantly higher platelet counts and platelet‐count corrected serum TXB2 than those with adequate inhibition. Eight patients with PV were sampled again after 12 ± 4 months, and had reproducible serum TXB2 and urinary TXM values. The in silico model predicted complete inhibition of platelet‐derived TXB2 by b.i.d. aspirin, a prediction verified in a patient with PV with the highest TXB2 value while on aspirin q.d. and treated short‐term with a b.i.d. regimen. In conclusion, one in three patients with PV on low‐dose aspirin display less‐than‐maximal inhibition of platelet TXA2 production. Serum TXB2 measurement can be a valuable option to guide precision dosing of antiplatelet therapy in patients with PV.

Thromboxane A 2 (TXA 2 ) is a biologically active metabolite of arachidonic acid formed by the action of the terminal synthase, thromboxane A 2 synthase (TXA 2 S), on prostaglandin endoperoxide (PGH 2 ). TXA 2 is responsible for multiple biological processes through its cell surface receptor, the T-prostanoid (TP) receptor. Thromboxane A 2 synthase and TP are the two necessary components for the functioning of this potent bioactive lipid. Thromboxane A 2 is widely implicated in a range of cardiovascular diseases, owing to its acute and chronic effects in promoting platelet aggregation, vasoconstriction, and proliferation. In recent years, additional functional roles for both TXA 2 S and TP in cancer progression have been indicated. Increased cyclooxygenase (COX)-2 expression has been described in a variety of human cancers, which has focused attention on TXA 2 as a downstream metabolite of the COX-2-derived PGH 2 . Several studies suggest potential involvement of TXA 2 S and TP in tumor progression, especially tumor cell proliferation, migration, and invasion that are key steps in cancer progression. In addition, the regulation of neovascularization by TP has been identified as a potent source of control during oncogenesis. There have been several recent reviews of TXA 2 S and TP but thus far none have discussed its role in cancer progression and metastasis in depth. This review will focus on some of the more recent findings and advances with a significant emphasis on understanding the functional role of TXA 2 S and TP in cancer progression and metastasis.

In the DEPOXIN project, we have found that a high ratio of omega-6/omega-3 fatty acids (FA) is associated with worsening of depressive symptoms in children and adolescents with depressive disorder (DD) and that the 12-week omega-3 FA supplementation modulates DD symptoms. Here we present our results of the secondary outcomes: the levels of thromboxane (TXB), brain-derived neurotrophic factor (BDNF), homocysteine (HCy) and vitamin D. Fifty-eight patients were randomized into two arms. One group received a fish oil emulsion enriched with omega-3 FA, and the other received a sunflower oil emulsion containing omega-6 FA, for 12 weeks. Depressive symptoms were evaluated, using the Child’s Depressive Inventory (CDI). The patients with DD had elevated TXB levels and decreased vitamin D levels, as compared to healthy controls. Both CDI and omega-6/omega-3 ratio correlated positively with TXB and negatively with BDNF at baseline. Compared to the omega-6 FA group, the supplementation with omega-3 FA for 12 weeks significantly reduced plasma TXB (p = 0.024) and increased BDNF (p = 0.011) levels. No changes in HCy and vitamin D were observed. Our results demonstrate the possible role of TXB and BDNF in the pathophysiology of DD and the benefits of omega-3 FA supplementation. The study was registered with the ISRCTN registry (ISRCTN81655012).

The thromboxane A receptor (TP), expressed in platelets and smooth muscle, plays an important role in blood clotting and muscle contraction. The endogenous ligand of this G protein-coupled receptor (GPCR), thromboxane A (TXA ), is a short-lived arachidonic acid metabolite with a half-life of ∼30 seconds, which makes investigating the TP structure and activation mechanism highly challenging. Here we determine the structures of the TP in complex with the synthetic agonists, U46619 and I-BOP, stable analogues of the natural ligand, in the presence of the signalling protein partner, G . The structures reveal a unique activation switch for the receptor that differs from typical class A GPCR family members. Complemented by functional studies, mutational analysis, docking, and molecular dynamics (MD) simulations, our investigation highlights the differences between agonist and antagonist binding and explores the ligand entry mechanism to the binding pocket from within the membrane via a molecular gate composed of two transmembrane helices. In addition, our study provides crucial information to aid in the rational design of compounds targeting the TP, and offers mechanistic insights into inherited disorders associated with mutations in the TP.

Aspirin is the dominant antiplatelet therapy for cardiovascular disease. Naproxen is frequently used in aspirin-treated patients and may influence the antiplatelet effect of aspirin. We evaluated the pharmacodynamic interaction (lower bound of the one-sided 95% CI for serum TxB2 inhibition < 95%) between 220 mg immediate-release naproxen sodium (once or twice daily) and 81 mg daily immediate release aspirin at various dosing intervals. There was no interaction during the first day of concurrent treatment. After 10 days, irrespective of the timing and dose of naproxen in relation to aspirin dosing, a pharmacodynamic interaction occurred which persisted after discontinuing naproxen. In the control group (aspirin alone), the lower bound for serum TxB2 inhibition was > 98% at all time points. The clinical relevance of these observations remains unknown and merits further investigation since over-the-counter naproxen is widely used to relieve pain by individuals taking low dose aspirin for cardioprotection.Clinical Trial Registration: NCT02229461

Prostaglandins (PGs) are lipid mediators belonging to the eicosanoid family. PGs were first discovered in mammals where they are key players in a great variety of physiological and pathological processes, for instance muscle and blood vessel tone regulation, inflammation, signaling, hemostasis, reproduction, and sleep-wake regulation. These molecules have successively been discovered in lower organisms, including marine invertebrates in which they play similar roles to those in mammals, being involved in the control of oogenesis and spermatogenesis, ion transport, and defense. Prostaglandins have also been found in some marine macroalgae of the genera Gracilaria and Laminaria and very recently the PGs pathway has been identified for the first time in some species of marine microalgae. In this review we report on the occurrence of prostaglandins in the marine environment and discuss the anti-inflammatory role of these molecules.

Modern functional imaging techniques of the brain measure local hemodynamic responses evoked by neuronal activity. Capillary pericytes recently were suggested to mediate neurovascular coupling in brain slices, but their role in vivo remains unexplored. We used two-photon microscopy to study in real time pericytes and the dynamic changes of capillary diameter and blood flow in the cortex of anesthetized mice, as well as in brain slices. The thromboxane A₂ analog, 9,11-dideoxy-9α, 11α-methanoepoxy Prostaglandin F2α (U46619), induced constrictions in the vicinity of pericytes in a fraction of capillaries, whereas others dilated. The changes in vessel diameter resulted in changes in capillary red blood cell (RBC) flow. In contrast, during brief epochs of seizure activity elicited by local administration of the GABA A receptor antagonist, bicuculline, capillary RBC flow increased without pericyte-induced capillary diameter changes. Precapillary arterioles were the smallest vessels to dilate, together with penetrating and pial arterioles. Our results provide in vivo evidence that pericytes can modulate capillary blood flow in the brain, which may be important under pathological conditions. However, our data suggest that precapillary and penetrating arterioles, rather than pericytes in capillaries, are responsible for the blood flow increase induced by neural activity.

There is increasing evidence that aspirin initiates biosynthesis of novel antiinflammatory mediators by means of interactions between endothelial cells and leukocytes. These mediators are classified as aspirin-triggered 15-epi-lipoxins. Such compounds may account at least in part for aspirin's clinical benefits, which are distinct from the well appreciated action of aspirin as a platelet inhibitor. Here, we addressed whether aspirin-triggered 15-epi-lipoxin A4 (ATL) formation is aspirin-dependent in humans and its relationship to aspirin's antiplatelet activity. We conducted a randomized clinical trial among 128 healthy subjects allocated to placebo or to 81-, 325-, or 650-mg daily doses of aspirin for 8 weeks. Plasma thromboxane ( TX) B2, an indicator of platelet reactivity, and ATL were assessed from blood collected at baseline and at 8 weeks. Plasma ATL levels significantly increased in the 81-mg aspirin group (0.25 ± 0.63 ng/ml, P = 0.04), with borderline increases in the 325-mg group (0.16 ± 0.71 ng/ml) and no apparent significant changes in the 650-mg group (0.01 ± 0.75 ng/ml, P = 0.96). When ATL and TXB2 were compared, levels changed in a statistically significant and opposite direction (P < 0.01) for all three aspirin doses. These results demonstrated that low-dose aspirin (81 mg daily) initiates production of antiinflammatory ATL opposite to the inhibition of TX. Monitoring ATL may represent a simple clinical parameter to verify an individual's vascular leukocyte antiinflammatory response with low-dose aspirin treatment. These results also emphasize the importance of cell-cell interactions in the modulation of hemostatic, thrombotic, and inflammatory processes.

Cardiovascular diseases are currently among the leading causes of morbidity and mortality in many developed countries. They are distinguished by chronic and latent development, a course with stages of worsening of symptoms and a period of improvement, and a constant potential threat to life. One of the most important disorders in cardiovascular disease is ischemic stroke. The causes of ischemic stroke can be divided into non-modifiable and modifiable causes. One treatment modality from a neurological point of view is acetylsalicylic acid (ASA), which blocks cyclooxygenase and, thus, thromboxane synthesis. The legitimacy of its administration does not raise any doubts in the case of the acute phase of stroke in patients in whom thrombolytic treatment cannot be initiated. The measurement of thromboxane B2 (TxB2) in serum (a stable metabolic product of TxA2) is the only test that measures the effect of aspirin on the activity of COX-1 in platelets. Measurement of thromboxane B2 may be a potential biomarker of vascular disease risk in patients treated with aspirin. The aim of this study is to present the role of thromboxane B2 in ischemic stroke and to present effective therapies for the treatment of ischemic stroke. Scientific articles from the PubMed database were used for the work, which were selected on the basis of a search for “thromboxane and stroke”. Subsequently, a restriction was introduced for works older than 10 years, those concerning animals, and those without full text access. Ultimately, 58 articles were selected. It was shown that a high concentration of TXB2 may be a risk factor for ischemic stroke or ischemic heart disease. However, there is insufficient evidence to suggest that thromboxane could be used in clinical practice as a marker of ischemic stroke. The inclusion of ASA in the prevention of stroke has a beneficial effect that is associated with the effect on thromboxane. However, its insufficient power in 25% or even 50% of the population should be taken into account. An alternative and/or additional therapy could be a selective antagonist of the thromboxane receptor. Thromboxane A2 production is inhibited by estrogen; therefore, the risk of CVD after the menopause and among men is higher. More research is needed in this area.