Thromboxane A2 Levels Research Articles

Mean platelet volume as a surrogate marker of inflammation in systemic lupus erythematosus

We have read the article published by Yavuz et al. with a great interest [1]. They examined the mean platelet volume (MPV) in children with systemic lupus erythematosus (SLE) at the active and inactive stages, and they compared it with healthy controls. They found that MPV was significantly higher in patients with SLE than in controls and significantly increased in active phase compared to inactive phase. This is the first study in this subject. On the other hand, we want to make minor criticism about this study from methodological aspect. Firstly, MPV measurement technique is not clear in the study. They did not mention about the tube in which MPV was measured. Is it citrate or ethylenediaminetetraacetic acid (EDTA) tube? They also did not mention about the time interval between blood sampling and analysis. This time interval is important if they used EDTA anticoagulated tubes. MPV increases over time in EDTA anticoagulated samples, and this increase was shown to be proportional with the delay in time between sample collection and laboratory analysis. This is not valid for citrate tube.With impedance counting, the MPV increases over time as platelets swell in EDTA, with increases of 7.9 % within 30 min having been reported and an overall increase of 13.4 % over 24 h, although the majority of this increase occurs within the first 6 h [2]. The recommended optimal measuring time of MPV is maximum 120 min after venipuncture. For reliable MPV measurement, the potential influence of anticoagulant on the MPV must be carefully controlled by standardizing the time delay between sampling and analysis (less than 2 h). Secondly, there are significant associations of MPV with many cardiovascular risk factors like smoking, obesity, hyperlipidemia, and metabolic syndrome [3]. They excluded hyperlipidemia, hypertension, and diabetes mellitus; however, they did not mention about the body mass index of patients and controls and proportion of patients and controls with metabolic syndrome. It has been shown that obesity and metabolic syndrome increase MPV values [3]. Absolutely, these factors should be considered in MPV assessment in children like adults. Platelet activation plays a major role in the pathophysiology of diseases prone to thrombosis and inflammation, and in line with this, MPV might be a link between thrombosis and inflammation [4]. It might be speculated that inflammation existing in patients with SLE might cause increased platelet reactivity as measured by MPV in these patients. MPV is universally available with routine blood counts by automated hemograms and a simple and easy method of assessing platelet function. In comparison to smaller ones, larger platelets have more granules, aggregate more rapidly with collagen, have higher thromboxane A2 level, and express more glycoprotein Ib and IIb/IIIa receptors [2, 5]. We believe that MPV can be affected bymany inflammatory and cardiovascular risk factors. Because of that, all confounding factors must be taken into account. In addition, standardized methods must be used in MPV measurement.

Decichine enhances hemostasis of activated platelets via AMPA receptors

Dencichine, one of the non-protein amino acids present in the roots of Panax notoginseng, has been found to shorten bleeding time of mice and increase the number of platelets. However, the exact underlying mechanisms have not been elucidated yet. This study was aimed to identify the hemostatic effect of dencichine and uncover its mechanisms. Hemostatic effect was assessed by measuring tail bleeding time and coagulation indices of rats. PT, APTT, TT and FIB concentration were measured using a Sysmex CA-1500 plasma coagulation analyzer. Platelet aggregation rate was determined by using a platelet aggregometer. Concentration of cyotosolic calcium was evaluated by Fluo-3 and levels of cyclic adenosine monophosphate (cAMP) and thromboxane A₂ (TXA₂) were measured by ELISA method. Dencichine administered orally shortened tail bleeding time, reduced APTT and TT but increased the concentration of FIB in plasma in a dose-dependent manner. When induced with trap, dencichine could elevate the cytoplasmic concentration of calcium, and secretion of TXA₂ as well as the ratio of TXA₂ to PGI₂ from platelets. Meanwhile, it decreased the level of intracellular cAMP. However, CNQX could block the enhanced hemostatic effect of dencichine. These results suggested that dencichine exerted hemostatic function via AMPA receptors on platelets, therefore, facilitated coagulation cascade in a paracrine fashion by control of platelet cytosolic calcium influx, cAMP production and TXA₂ release. Current study may contribute to its clinical use in therapy of hemorrhage.

Effects of all-trans retinoic acid on signal pathway of cyclooxygenase-2 and Smad3&7 in transforming growth factor-β-stimulated glomerular mesangial cells

All-trans retinoic acid (ATRA) has been used for the treatment of acute promyelocytic leukemia. It remains unclear, however, whether ATRA affects cyclooxygenase-2 (COX-2; an enzyme involved in prostaglandin production), PGE2, and thromboxane A2 (TXA2) (metabolic products of COX-2) by a transforming growth factor-β/Smad-signaling pathway, which plays important roles in mesangial-cell proliferation and renal fibrosis. In this study, the mRNA and protein of Smad3, Smad7, and COX-2 were detected by reverse transcription-polymerase chain reaction and Western blot, respectively, in mesangial cells stimulated by transforming growth factor-β (TGF-β) and treated with ATRA at various concentrations and times. The protein level of PGE2 and TXA2 was also measured by enzyme-linked immunosorbent assay. The localization of Smad3 and Smand7 was observed by confocal microscope. Cell proliferation was detected by MTT assay, while apoptosis was determined using Hoechest staining. The expression of Smad3, Smad7, and COX-2 mRNA and protein was increased by exogenous TGF-β, but inhibited by pretreatment of ATRA, in dose and time-dependent manners. In addition, the expression of Smad3 and Smad7 was significantly reduced not only by staurosporine, an inhibitor of threonine/serine protein kinases as well as smad, but also by NS-398, an inhibitor of COX-2. PGE2 and TXA2 were raised by TGF-β, but also decreased by ATRA, staurosporine, and NS-398. Moreover, ATRA reversed the translocation of Smad3 and Smad7 induced by TGF-β. Compared with the control, TGF-β also significantly enhanced proliferation and inhibited apoptosis of mesangial cells. ATRA dose-dependently inhibited TGF-β-induced cell proliferation, but had no significant effect on apoptosis in rat mesangial cells. Therefore, ATRA repressed COX-2, PGE2, and TXA2 via the TGF-β/Smad-signaling pathway and inhibited mesangial-cell proliferation, which might subsequently prevent renal fibrosis.

Changes in Plasma Levels of Vasoactive Factors in Patients Undergoing Abdominal Surgery

Background: To investigate the changes in plasma levels of endothelin (ET), nitric oxide (NO), prostacyclin (PGI2) and thromboxane A2 (TXA2) in patients undergoing abdominal operation. Materials and Methods: Thirty cases of abdominal surgery (14 males, 16 females; mean age 48 ± 11 years, ranging from 24 to 70) were prospectively recruited: Twenty-four cases of cholelithiasis and cholecystitis, 2 cases of peptic ulcer and 4 cases of portal vein hypertension. At five different time points (1-3 days after hospitalization (T1), at surgery beginning, after anesthesia (T2) and at the first (T3), third (T4) and fifth day (T5) after surgery), plasma levels of ET-1, NO2-, NO3-, 6-keto-PGF1α and thromboxane B2 (TXB2), the latter two being stable metabolites of PGI2 and TXA2 respectively, were measured. Results: ET-1 levels increased significantly after anesthesia and surgery (T1 = 69.2 ± 10.7 vs. T2 = 82.4 ± 14.7 vs. T3 = 96.6 ± 22.8 pg/ml, p 2 levels before surgery were significantly lower than that after (T2 = 67.5 ± 52.7 vs. T3 = 157.6 ± 21.8 pg/ml, p 1α were significantly higher than that after anesthesia and surgery (T1 = 180.5 ± 17.8 vs. T2 = 132.1 ± 32.6 vs. T3 = 110.9 ± 31.9 pg/ml, p 2) increased significantly after surgery, while vasodilatory factors (NO and PGI2) decreased significantly after operation. Imbalance in vasoactive factors encourages hypercoagulability and then may play a role in the pathobiology of post-surgery complications, such as deep venous thrombosis (DVT).

The significance of natriuretic peptide in treatment of pulmonary hypertension after mitral valve replacement

To compare the therapeutic efficacy of recombinant human brain natriuretic peptide and prostaglandin E1 in the treatment of pulmonary hypertension after mitral valve replacement. Sixty patients with postoperative pulmonary hypertension were divided randomly into 3 groups that received saline, prostaglandin E1, and natriuretic peptide infusions for 12 hours each. The hemodynamics data were monitored consecutively, and the levels of thromboxane A2 and cyclic guanosine monophosphate were detected pretreatment, after treatment, and 1 week after surgery. The arterial pressure, pulmonary arterial pressure, and pulmonary capillary wedge pressure decreased 1hour after prostaglandin E1 treatment and rebounded after treatment discontinuation. The pulmonary arterial pressure and pulmonary capillary wedge pressure in the natriuretic peptide group decreased 3 hours after treatment; pulmonary arterial pressure decreased less than that of the prostaglandin group, and there was no evidence of hemodynamic rebound after treatment discontinuation. The natriuretic peptide had no significant effects on arterial pressure. In both the prostaglandin and natriuretic peptide groups, cyclic guanosine monophosphate increased after the treatment, which was even higher in the latter group. Prostaglandin E1 could lead to the decrease of thromboxane A2, which was not seen in the natriuretic peptide group. Both brain natriuretic peptide and prostaglandin E1 can effectively reduce pulmonary hypertension; however, natriuretic peptide has a slower and milder efficacy. The effects of these 2 drugs in reducing thepulmonary arterial pressure may be mediated through different pathways.

Wild blueberry consumption affects aortic vascular function in the obese Zucker rat

This study evaluates the effect of wild blueberry (WB) consumption on the biomechanical properties of the aorta in the obese Zucker rat (OZR), a model of the metabolic syndrome. Thirty-six OZRs and 36 lean controls (lean Zucker rats) were placed either on a WB-enriched or a control (C) diet for 8 weeks. Phenylephrine (Phe)-mediated vasoconstriction and acetylcholine (Ach)-mediated vasorelaxation in the aortic vessel were investigated, as well as the contribution of the nitric oxide synthase and cyclooxygenase (COX) pathways in each of the above responses by using specific inhibitors. Obese Zucker rats exhibited a reduced vasocontstrictor response to Phe and an exaggerated vasorelaxant response to Ach. The WB diet partially restored Phe-induced constrictor responses and attenuated Ach-induced relaxant responses in OZR. Plasma nitric oxide was significantly attenuated (22.1 ± 1.1 μmol·L(-1), WB vs 25.6 ± 1.4 μmol·L(-1), C, p ≤ 0.05) with the WB diet. Thromboxane A2 levels in the aortic effluent were not significantly affected in the WB diet group, while PGI2 concentration significantly increased (766.5 ± 92.2 pg·mg(-1) aorta in the WB vs 571.7 ± 37.8 pg·g(-1) aorta in the C group, p ≤ 0.05). Downregulation of inducible nitric oxide synthase and COX2 expression in the OZR aorta was observed in the WB diet group. In conclusion, WB consumption altered the biomechanical properties of the OZR aorta by partially restoring the impaired Phe-induced constrictor responses and attenuating the exaggerated response to Ach-induced vasorelaxation.

Mean platelet volume can be affected by many confounding factors in chronic periodontitis

We read the article published by Androsz-Kowalska et al. [1] with great interest. They investigated the mean platelet volume (MPV) in patients with chronic periodontitis with coronary artery disease (CAD), chronic periodontitis without CAD, and control subjects. They found that MPV was significantly higher in patients with chronic periodontitis with CAD than in controls. However, there was no significant difference between patients with chronic periodontitis without CAD and controls. In this study, there was a significant correlation between periodontal parameters and MPV. They concluded that chronic periodontitis in patients with CAD results in an increased MPV. This is a well designed and written study. On the other hand, please allow us to make a minor criticism about this study from a methodological point of view. There are significant associations of MPV with type 2 diabetes mellitus, prediabetes, smoking, hypertension, hypercholesterolaemia, obesity, coronary heart disease, metabolic syndrome, statins and some antihypertensive use and atrial fibrillation [2]. There are also significant associations of MPV and inflammatory diseases including rheumatic diseases [3]. The authors did not mention body mass index, systolic and diastolic blood pressure, smoking status, glucose and cholesterol levels or antihypertensive drug use in patients and control subjects. Patients with chronic periodontitis with CAD could be supposed to have more cardiovascular risk factors; these in turn increase MPV. It would be better if the authors had mentioned these confounding factors. It has been shown that some antihypertensive drugs can decrease MPV values [4]. It would also be useful if the authors had provided data about the antihypertensive drug use which can influence MPV values. MPV is universally available with routine blood counts and is a simple and easy method of assessing platelet function. Compared to smaller ones, larger platelets have more granules, aggregate more rapidly with collagen, have higher thromboxane A2 level, and express more glycoprotein Ib and IIb/IIIa receptors [5]. MPV is becoming an increasingly popular diagnostic marker. It is also associated with many confounding markers as mentioned before. In chronic periodontitis, there is chronic low grade inflammation. In this state, we can expect higher MPV values, even in the absence of CAD. High MPV values are associated with low grade inflammatory conditions in addition to a variety of established risk factors, forcardiovascular and cerebrovascular disorders [3]. Studies with a large sample size and with better control of the confounding factors affecting MPV are needed to clarify the relationship between chronic periodontitis, MPV and cardiovascular diseases.

Protection of vascular endothelium by aspirin in a murine model of chronic Chagas’ disease

Chronic Chagas' disease affects 10-30 % of patients infected with Trypanosoma cruzi, and it mainly manifests as cardiomyopathy. Important pathophysiological mechanisms involved in the cardiac lesions include activation of the endothelium and induced microvascular alterations. These processes involve the production of endothelial adhesion molecules and thromboxane A2, which are involved in inflammatory cell recruitment and platelet aggregation, respectively. Cyclooxygenase inhibitors such as aspirin decrease thromboxane production and alter the course of Chagas' disease, both in the acute and chronic phases. We studied the effects of the administration of low and high doses of aspirin during the early phase of T. cruzi infection, following microvascular damage in the context of a chronic murine model of Chagas' disease. The effects of both schedules were assessed at 24 and 90 days postinfection by evaluating parasitemia, mortality, and cardiac histopathological changes as well as the expression of ICAM, VCAM, and E-selectin in cardiac tissue. Thromboxane A2, soluble ICAM, and E-selectin blood levels were also measured. While aspirin did not affect parasitemia or mortality in the infected mice, it decreased both cardiac inflammatory infiltrates and thromboxane levels. Additionally, at 90 days postinfection, aspirin normalized sICAM and sE-selectin levels. Considering the improved endothelial function induced by aspirin, we propose the possibility of including this drug in clinical therapy to treat chronic Chagas' disease.

The Effects of AT1 Receptor Blockade on Skin Microcirculatory Blood Flow and Thromboxane A2 (TXA2) Production in Young Healthy Women

AT1 receptor activation has an important role in maintaining the vascular release of prostaglandins responsible for mediating hypoxic dilation in skeletal muscle microvessels in normotensive rats. High salt diet leads to impairment of vasodilator responses that could be restored by infusion of subpressor dose of ANG II via its interaction with AT1 receptors. In addition to AT1 receptors blockade, losartan blocks thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor. The aim of this study was to determine the effect of one week AT1 receptor blockade by losartan in 10 healthy normotensive women (20±2 years old) on law salt diet (LSD) on post occlusive hyperemic blood flow response in skin microcirculation by Laser Doppler Flowmetry (LDF) and to determine the plasma renin activity (PRA) and plasma thromboxane A2 (TXA2) concentration. Participants maintained LSD (<40 mmol of Na/day) and took 50 mg of losartan/day for 7 days. After one week of losartan administration the post occlusive hyperemic tissue blood flow was unchanged. However, plasma PRA and TXA2 levels were significantly increased compared to pre‐losartan values. Our results indicate that although one week of AT1 receptor blockade increases the plasma TXA2 concentration and PRA, the skin microcirculatory blood flow remained unchanged, possibly due to losartan blockade of TXA2 receptors and ANG II interaction with AT2 receptors.

Effects of menopausal hormone treatments on prostanoid levels and platelet sensitivity to cyclic AMP activation in healthy, recently menopausal women

Estrogen modulates the prostanoids prostacyclin (PGI2) and thromboxane A2 (TXA2) which contribute to vascular hemostasis in endothelium and platelets. Estrogen decreases in women at menopause, and menopausal hormone therapy (MHT) may increase risk of thrombosis. This study aimed to determine effects of MHT on serum prostanoid levels and on prostanoid‐related platelet functions in healthy, recently‐menopausal women. Women (age 52.3±2.3 yrs; n=115) enrolled in the Kronos Early Estrogen Prevention Study (KEEPS) were randomized to either: 1) oral conjugated equine estrogen, 2) transdermal 17β estradiol each with intermittent oral progesterone or 3) placebo, for 48 months. Serum PGI2 and TXA2 levels were assessed by quantification (ng/ml) of their stable metabolites 6‐k‐PGF1α and TXB2, respectively. Initial TXB2 levels (46.9±7.5) were unchanged (P>; 0.05) after 48 months in each treatment group. However, 6‐k‐PGF1α decreased from 2.1±0.2 to 1.4±0.1 at 48 months in combined groups, but was statistically significant (1.5±0.3) only in the transdermal group. Inhibition of platelet ATP secretion by PGE1 did not correlate with serum 6‐k‐PGF1α levels. These results suggest that serum PGI2 levels decrease with age in menopausal women and are unaffected by MHT. Factors other than changes in serum prostanoids may impose thrombotic risk associated with MHT. (Supported by the Aurora Fnd, NIH HL88988 and Mayo Clinic).

Wild blueberry‐enriched diet affects α1‐adrenergic induced vasoconstrictor response in the aorta of obese Zucker rats

This study investigates the effects of wild blueberry (WB, Vaccinium angustifolium) on arterial contractile response to the α1‐adrenergic agonist phenylephrine (Phe) in 8 week old obese Zucker rats (OZR). Twenty OZR were randomly assigned to a control (C) or an 8% WB diet for 8 weeks. Vascular studies were conducted in isolated aortic ring preparations to measure vasoconstriction induced by Phe, 10–8 to 3×10–6M. Plasma nitric oxide (NO) and aortic concentration of prostacyclin (PGI2) and thromboxane A2 (TXA2) in the effluent was determined.Obese Zucker rats exhibited a reduced response to Phe‐induced vasoconstriction, possibly due to a compensatory overproduction of NO under inflammatory conditions. The WB diet partially restored Phe‐induced constrictor responses, compared to their lean littermates, by increasing the maximal force developed (0.55±0.02 g WB vs 0.43±0.02 g C, p≤0.05)Plasma NO was significantly attenuated (22.1±1.1 μmol/L, WB vs 25.6±1.4 μmol/L, C, p≤0.05) with the WB diet. Aortic effluent TXA2 levels were not significantly altered, while PGI2 concentration significantly increased (766.5±92.2 pg/mg WB vs 571.7±37.8 pg/g C aorta, p≤0.05).In conclusion, WB consumption significantly altered vasomotor tone in response to an α1‐adrenergic agonist in the OZR aorta and modulated plasma NO and aortic effluent PGI2.Grant Funding Source: Wild Blueberry Association of North America

Benznidazole prevents endothelial damage in an experimental model of Chagas disease

To evaluate the effect of benznidazole on endothelial activation in a murine model of Chagas disease. A low (30mg/kg/day) and a high (100mg/kg/day) dose of benznidazole were administered to mice infected with Trypanosoma cruzi during the early phases of the infection. The effects of the treatments were assessed at 24 and 90 days postinfection by evaluating the parasitaemia, mortality, histopathological changes and expression of ICAM in the cardiac tissue. The blood levels of thromboxane A2, soluble ICAM and E-selectin were also measured. T. cruzi clearance was assessed by the detection of parasite DNA in the heart tissue of infected mice. Benznidazole decreased the cardiac damage induced by the parasite, and amastigote nests disappeared at 90 days postinfection. Both doses cleared the parasite from the cardiac tissue at 24 and 90 days postinfection. In addition, benznidazole decreased the thromboxane levels and normalized the plasma sICAM and sE-selectin levels by 90 days postinfection. Early administration of benznidazole at a dose as low as 30mg/kg eradicates T. cruzi from cardiac tissue. Additionally, benznidazole prevents cardiac damage and modulates endothelial activation as part of its antichagasic activity.

English

Introduction Thrombocytopenia, or a low blood platelet count, is encountered in 7–8% of all pregnancies1. It is the second most common blood disorder in pregnancy2,3. The first blood disorder is anaemia3. Platelets are non-nucleated cells derived from megakaryocytes in the bone marrow and normally live in the peripheral circulation for as long as 10 days. Platelets play a critical initiating role in haemostatic system1,4. The normal range of platelets in non-pregnant women is 150 000– 400 000/μL. Average platelet count in pregnancy is decreased. Change in platelet count is due to haemodilution, increased platelet consumption and increased platelet aggregation driven by increased levels of thromboxane A2. Thrombocytopenia can be defined as platelet count less than 150 000/μL or platelet count below the 2.5th percentile for pregnant patients (116 000/μL)1. Classification of thrombocytopenia in pregnancy is arbitary and not necessarily clinically relevant. Mild thrombocytopenia is 100 000– 150 000/μL, moderate thrombocytopenia is 50 000–100 000/μL and severe thrombocytopenia is less than 50 000/μL. The pathophysiology of gestational thrombocytopenia (GT) is unknown. It usually develops in the third trimester, detected incidentally, pati ents are asymptomatic with no prepregnancy history of low platelets or abnormal bleeding, it is mild thrombocytopenia (counts more than 70 000/μL)5–9. GT accounts for almost threefourths of all cases of thrombocytopenia2,10. Mode of delivery is determined by obstetric/maternal indications. Platelet counts normalize within 2–12 weeks following delivery10–12. No pathological significance for the mother or foetus is noted. No risk for foetal haemorrhage or bleeding complications is observed13–17. A low platelet count can also be associated with preeclampsia, HELLP syndrome or idiopathic thrombocytopenic purpura (ITP)18–23. The differential diagnosis between mild ITP and GT is very difficult during pregnancy5,19. ITP accounts for only approximately one case of thrombocytopenia per 1000 pregnancies and 5% of cases of pregnancy-associated thrombocytopenia, it is the most common cause of significant thrombocytopenia in the first trimester24–27. Women with ITP often have a history of bleeding complications and have thrombocytopenia on a prepregnancy platelet count16,28. We present this rare case of GT in a pregnant 30-year-old woman.

Endothelium dependent expression and underlying mechanisms of des-Arg9-bradykinin-induced B1R-mediated vasoconstriction in rat portal vein

Endothelial dysfunction has been implicated in portal vein obstruction, a condition responsible for major complications in chronic portal hypertension. Increased vascular tone due to disruption of endothelial function has been associated with an imbalance in the equilibrium between endothelium-derived relaxing and contracting factors. Herein, we assessed underlying mechanisms by which expression of bradykinin B(1) receptor (B(1)R) is induced in the endothelium and how its stimulation triggers vasoconstriction in the rat portal vein. Prolonged in vitro incubation of portal vein resulted in time- and endothelium-dependent expression of B(1)R and cyclooxygenase-2 (COX-2). Inhibition of protein kinase C (PKC) or phosphatidylinositol 3-kinase (PI3K) significantly reduced expression of B(1)R through the regulation of transcription factors, activator protein-1 (AP-1) and cAMP response element-binding protein (CREB). Moreover, pharmacological studies showed that B(1)R-mediated portal vein contraction was reduced by COX-2, but not COX-1, inhibitors. Notably, activation of endothelial B(1)R increased phospholipase A(2)/COX-2-derived thromboxane A(2) (TXA(2)) levels, which in turn mediated portal vein contraction through binding to TXA(2) receptors expressed in vascular smooth muscle cells. These results provide novel molecular mechanisms involved in the regulation of B(1)R expression and identify a critical role for the endothelial B(1)R in the modulation of portal vein vascular tone. Our study suggests a potential role for B(1)R antagonists as therapeutic tools for diseases where portal hypertension may be involved.

Abstract 4013: The positive role of TPγ in the induction of COX-2, TxA2 and cell growth by NNK in human lung cancer cells

Abstract Many studies have shown that 4-Methylnitrosamino-1-3-pyridyl-1-butanone (NNK), the most potent carcinogen present in tobacco smoke, can induce lung tumor growth. We previously demonstrated that the activation of extracellular regulated protein kinases (ERK) and cAMP response element-binding protein (CREB) is responsible for the pro-survival and proliferative effects of thromboxane A2 (TxA2) and its receptor (TP) in the human lung cancer cells stimulated with NNK (reported in oncogene journal). In current study, we further determined the role of cyclooxygenase(COX)-2/TxA2/TP pathway in lung cancer cell growth mediated by NNK. TP exists as two isoforms, ≤ and β, in human beings. Western blotting showed that TPα, but not TPα, was widely expressed in a series of human lung cells. NCI-H23 and CRL-2066, which express both TPγ and TPα, were selected as models in this study. COX-2 inhibitor NS398 could significantly reduce NNK-stimulated TxA2 synthesis. Moreover, NS398 and BM567, an agent combining TxA2 synthase inhibition and TP antagonism, had the similar effects to reverse NNK-induced activation of ERK and CREB and the increase in cell growth. Furthermore, the administration of TxA2 mimetic U46619 could almost reconstituted NNK-induced ERK and CREB activation in the presence of COX-2-siRNA. Collectively, these findings suggest that in lung cancer cells stimulated with NNK, TxA2 is mainly derived from COX-2 and acts as a key mediator for tumor-promoting effects of COX-2. Interestingly, TP antagonist SQ29548 could inhibit NNK-induced COX-2 protein expression and TxA2 production, indicating that TP is able to modulate NNK-induced COX-2 expression and activity, thereby constituting an auto-amplification mechanism of TxA2 synthesis in lung cancer cells stimulated with NNK. We further examined which TP isoform contributes to the NNK effects. We observed that the protein expression of TPα, but not TPα, was time-dependently increased by NNK. Moreover, the activation of ERK and CREB and the production of COX-2 and TxA2 by NNK were potentiated in cells transfected with pcDNA3-TPγ as compared with cells transfected with control vector or pcDNA3-TPα, and such effects could be reversed by SQ29548. However, in cells transfected with pcDNA3-TPα, the COX-2, TxA2, phospho-ERK and phospho-CREB levels were similar to that seen in the cells transfected with control vector, and neither NNK nor SQ29548 had any additional effects when compared to the control cells. Taken together, these data strongly suggest that TPγ rather than TPγ is, at least in part, responsible for the induction of COX-2, TxA2 and cell growth by NNK in lung cancer cells. Our study implies that targeting TxA2 and its receptor TPγ may represent a promising strategy for prevention of smoking-associated lung cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4013. doi:1538-7445.AM2012-4013

Predictors of thromboxane levels in patients with non-ST-elevation acute coronary syndromes on chronic aspirin therapy

High levels of thromboxane A2 (TxA2), a key mediator of platelet activation and aggregation, are associated with an increased risk of cardiovascular events. We aimed at assessing the predictors of higher plasma levels of TxB2, the stable metabolite of TxA2, in consecutive patients presenting with non-ST-elevation acute coronary syndrome (NSTE-ACS) on previous aspirin (ASA) treatment undergoing coronary angiography. Ninety-eight consecutive patients (age 61 ± 11, 75% males) with NSTE-ACS, on previous chronic ASA treatment, were prospectively enrolled in this study. Coronary disease extent was assessed by angiography according to the Bogaty score. In all patients, admission plasma levels of TxB2 (pg/ml) were measured by enzyme-linked immunosorbent assay, and patients showing TxB2 levels in the fourth quartile were compared to patients showing TxB2 levels in the lower quartiles. Multivariable logistic regression analysis showed that platelet count (odds ratio [OR] 1.18, 95% confidence interval [CI] 1.02-1.63, p=0.04), multivessel coronary disease (OR 1.37, 95% CI 1.13-3.67, p=0.03), and coronary atherosclerosis extent index (OR 1.91, 95% CI 1.45-6.79, p=0.001) were independent predictors of TxB2 level upper quartile. Of note, C-reactive protein serum levels were similar in patients with TxB2 levels in the upper quartile as compared to those in the lower quartiles (p=0.49). In conclusion, NSTE-ACS patients with severe coronary atherosclerosis may have incomplete suppression of TxA2 production despite chronic ASA therapy. This finding suggests that additional efforts should be made to lower TxA2 levels in patients with widespread coronary artery disease.

Study the levels of nitric oxide (NO), thromboxane A2 (TXA2), prostaglandin E2 (PGE2) and prostacycline (PGI2) in plasma of normal peregnant and preeclampsia women

study the levels of nitric oxide (NO), thromboxane A2 (TXA2), prostaglandin E2 (PGE2) and prostacycline (PGI2) in plasma of normal peregnant and preeclampsia women

Thromboxane Production in Morbidly Obese Subjects

Postmortem studies have demonstrated that morbidly obese subjects, surprisingly, have less coronary atherosclerosis than obese subjects. However, the reasons for this apparent protection from atherosclerosis are not yet clear. Thromboxane A2, a marker of platelet activation, is greater in obese subjects than in lean subjects, and this might be a clue to their increased cardiovascular risk. However, data on thromboxane A2 in morbidly obese subjects are lacking; therefore, we hypothesized that lower levels of thromboxane A2 in morbidly obese subjects might play a role in their lower atherothrombotic burden. We measured the serum levels of thromboxane B2 (TxB2), a stable metabolite of thromboxane A2, high-sensitivity C-reactive protein (hs-CRP) and leptin in 17 lean subjects (body mass index [BMI] 22.9 ± 1.6 kg/m(2)), 25 obese subjects (BMI 32.6 ± 2.4 kg/m(2)), and 23 morbidly obese subjects (BMI 48.6 ± 7.1 kg/m(2)), without insulin resistance, diabetes, or overt cardiovascular disease. The serum TxB2 levels were lower in the lean subjects than in the obese subjects (p = 0.046) and in the morbidly obese subjects than in the lean and obese subjects (p = 0.015 and p <0.001, respectively). In contrast, the hs-CRP and leptin levels were greater in the obese than in the lean subjects (hs-CRP, p <0.001; leptin, p <0.001) and in the morbidly obese subjects than in the lean subjects (p <0.001 for both). Leptin was also higher in the morbidly obese subjects than in the obese subjects (p <0.001). TxB2 negatively correlated with leptin and BMI. hs-CRP correlated with leptin, and both also correlated with waist circumference, BMI, and homeostasis model assessment of insulin-resistance. In conclusion, insulin-sensitive morbidly obese subjects had lower levels of TxB2 than the obese subjects and lean subjects, suggesting that reduced platelet activation could play a role in the paradoxical protection of morbidly obese subjects from atherosclerosis, despite the greater levels of leptin.

Roles of Thromboxane A2 On High Salt Induced-Fetal Defect.

Abstract Abstract 5129 Introduction Preeclampsia is a pregnancy-induced disorder. If a pregnant woman suffered from preeclampsia, her worse developed-placenta might result in growth retardation of the fetus, and in the most severe cases, it would cause fetal and maternal death. Several previous studies showed that circulating thromboxane A2 in preeclampsic women was higher than that of normal pregnant women, and higher thromboxane A2 level might induce thrombosis and hypertension in these patients. Thus, thromboxane A2 was thought to be an important metabolite relevant to the development of preeclampsia. Materials and Methods In order to clearly clarify the roles of thromboxane A2 on preeclampsia, wild type and thromboxane A2 synthase knockout pregnant mice were fed with drinking water containing high concentration of sodium chloride. The effect of thromboxane A2 on preeclampsia was observed by measuring blood pressure, urinary protein, systemic edema in pregnant mice, and placenta weight, fetal weight, fetal size and fetal sections were also measured and stained. Results In the groups of pregnant mice fed with high salt, maternal body weight, fetal size and fetal weight were severely decreased in wild type mice as compared to thromboxane A2 synthase knockout mice. Furthermore, abnormal cell degeneration was observed in fetus of wild type pregnant mice, but less in thromboxane A2 synthase knockout fetus. Conclusions These results demonstrate that knockout pregnant mice were more resistant to high salt treatment, implying the roles of thromboxane A2 on the development of maternal and fetal defects during high salt treatment. Disclosures No relevant conflicts of interest to declare.

Long-Acting Local Anesthetics Attenuate FMLP-induced Acute Lung Injury in Rats

Endothelin-1 (ET-1) is a mediator of lung diseases and a potent pulmonary vasoconstrictor. In addition to thromboxane A2, it participates in the formation of lung edema. Both lidocaine and mepivacaine attenuate the increase of pulmonary arterial pressure (PAP) and lung edema development. We examined the effects of procaine, bupivacaine, and ropivacaine on experimentally evoked PAP increase and ET-1 release. PAP and lung weight were measured in isolated rat lungs during perfusion with Krebs-Henseleit hydroxyethyl starch buffer. Bupivacaine, ropivacaine, or procaine was added to the solution at concentrations of 10(-2)-10(-7) mg/kg. ET-1 levels were measured in the perfusate by enzyme-immunoassay, and thromboxane A2 levels were assayed by radioimmunoassay. N-formyl-L-leucine-methionyl-L-phenylalanine was used to activate human polymorphonuclear neutrophils. Bupivacaine, ropivacaine, and procaine significantly attenuated increases of PAP (P < 0.05) and resulted in a reduction of lung weight in these treatment groups compared with the sham group (P < 0.05). The long-acting anesthetics bupivacaine and ropivacaine (P < 0.05), but not procaine, reduced ET-1 levels, produced low inflammation rates, and did not affect lung structures at doses from 10(-3) to 10(-6) mg/kg. Bupivacaine and ropivacaine attenuated N-formyl-L-leucine-methionyl-L-phenylalanine-induced PAP, reduced lung edema, and diminished ET-1 release. Lidocaine and mepivacaine are more effective in reducing PAP and edema formation, but long-acting local anesthetics also inhibit ET-1 depletion and therefore have increased anti-inflammatory properties.