TXB2 Levels Research Articles

Parecoxib Sodium does not Impair Platelet Function in Healthy Elderly and Non-Elderly Individuals

To compare the effects of parecoxib sodium, an injectable prodrug of a cyclo-oxygenase-2—specific inhibitor, and ketorolac on platelet function and bleeding time in elderly individuals and non-elderly adults. Double-blind, randomised, active- and placebo-controlled, parallel-group studies. Healthy men and women, between the ages of 65 and 95 years (62 elderly individuals) or 18 and 55 years (48 non-elderly individuals). Participants received placebo or active medication: parecoxib sodium 40mg twice daily intravenously for 8 days (both studies), ketorolac 15mg four times daily intravenously for 5 days (elderly individuals) or 30mg four times daily intravenously for 5 days (non-elderly individuals). Ex vivo platelet aggregation responses to arachidonate, collagen and adenosine diphosphate (ADP), bleeding time and serum thromboxane B2 (TXB2) levels were measured. In both studies, parecoxib sodium had little or no effect on arachidonate-induced platelet aggregation, whereas ketorolac caused statistically significant and sustained decreases in platelet aggregation throughout the entire drug administration period. Parecoxib sodium also had little or no effect on collagen- or ADP-induced aggregation compared with ketorolac. Although there was a high degree of variability in bleeding times, significant prolongation of bleeding times was observed only in the ketorolac groups in both studies. Parecoxib sodium had no effect on serum TxB2 concentrations in non-elderly individuals. In elderly individuals, ketorolac significantly and profoundly reduced TxB2 levels at all assessments, whereas parecoxib sodium showed less of a reduction. Although a direct correlation has not been proven, patients with reduced platelet function do appear to be at a higher risk of experiencing increased bleeding during surgery. Thus, the absence of effect on platelet aggregation and bleeding time observed in these studies suggests that parecoxib sodium is less likely to be associated with excessive bleeding during surgery, and therefore is potentially safer than ketorolac for use in patients undergoing surgery, irrespective of age.

Effects of chinese angelica root on plasma thromboxane A2 and prostacyclin in essential hypertension patients

Thromboxin A2(TXA2) and prostacyclin(PGI2) are intimately related with the genesis and development of essential hypertension(EH).Some studies proved that Chinese angelica root was a regulator on the balance of TXA2 and PGI2. In order to look for a new, effective therapy to prevent and treat hypertension, from November 1996 to August 1997, the level of plasma TXB2 and 6-keto-PGF1α in 60 EH patients were investigated to determine whether the above parameters were altered after being treated with Chinese angelica root.The results were reported as follows……

Time-Dependent Variations in Serum Nitrite, 6-Keto-Prostaglandin F1α and Thromboxane B2 Levels Induced by Lipopolysaccharide in Mice

Clinical features of certain immuno-inflammatory disorders exhibit time-dependent fluctuations, which could be related to circadian rhythmicity of proinflammatory mediator production. Many biologically active substances including nitric oxide (NO) and eicosanoids are released into the circulation in sepsis. Increased NO and eicosanoid levels have been reported to be responsible from death in septic shock. The aim of this study was to investigate the variations in the NO and eicosanoid production and mortality induced by bacterial endotoxin, lipopolysaccharide (LPS) injected either in the morning or in the evening. Experiments were performed on mice synchronised to 12 h light and 12 h dark (lights on at 09:00 h). Animals were injected intraperitoneally with LPS (10 mg/kg) at 09:00 (morning) and 21:00 h (evening) alone or in combination with aminoguanidine (NO synthase (NOS) inhibitor) (100 mg/kg) or indomethacin (cyclooxygenase (COX) inhibitor) (100 mg/kg). The serum was separated from blood samples obtained at nine different time points. Nitrite (stable product of NO), 6-keto-prostaglandin F1α (6-keto-PGF1α, stable product of prostacyclin) and thromboxane B2 (TxB2, stable product of thromboxane) concentrations in serum samples were measured. Serum nitrite levels showed a 24 h circadian rhythmicity depending on LPS injection time. Morning injection caused a peak after 15 h, while evening injection had two peaks after 9 and 18 h. The peak values obtained from morning and evening injections were significantly decreased by aminoguanidine and indomethacin. When LPS injected to mice in the morning and in the evening, it gradually increased the mortality rate within 24 h which could be abolished by aminoguanidine, but not indomethacin. Indomethacin-induced inhibition on LPS-induced nitrite levels was higher in the morning than in the evening. 6-keto-PGF1α and TxB2 levels were decreased by indomethacin when injected with LPS at both injection times, but not aminoguanidine. These results showed that there is an interaction between NO and eicosanoids, and LPS may produce different effects on NOS activity, but not eicosanoid production and mortality, depending on injection time in the experimental septic shock model in mice. Chronopharmacological manipulations of NOS and COX pathways and interactions between them could lead to novel therapeutic approaches for the treatment of septic shock.

Determination of eicosanoid and cytokine production in salvaged blood, stored red blood cell concentrates, and whole blood

Study Objective: To determine the production of the eicosanoids prostaglandin 2 (PGE2) and thromboxane 2 (TxB2) and the cytokines interleukin 1 beta (IL-1-β) and interleukin 6 (IL-6) in whole blood (WB), unfiltered red blood cell (RBC), and filtered RBC concentrates, and salvaged blood. Design: Prospective study. Setting: University hospital of Erlangen. Patients: 32 healthy volunteers and 14 ASA physical status I, II, and III radical prostatectomy patients (mean age 65 yrs). Interventions: Sixteen WB units and 16 RBC units (divided into 16 filtered and unfiltered units each) were taken from 32 volunteers. Fourteen salvaged RBC units were obtained from the 14 radical prostatectomy patients. Sixteen WB units were stored for 35 days. From the 16 WB donations, RBC concentrates (PAGGS-M) were prepared. The RBC concentrates were halved, one half had its leukocytes removed at day 0; both halves were stored for 49 days. Salvaged blood (n = 14) was stored up to 2 hours during surgery and then retransfused. Measurements and Main Results: Immediately at the start of the study, in all blood units (WB, RBC filtered, and RBC unfiltered units) at days 0 and 21, and at the end of the storage period (WB: 35 days, RBC concentrates: 49 days) and in the salvaged RBC units, the following parameters were measured: PGE2, TxB2, IL-1-β, IL-6, hematocrit, platelet number, leukocytes, blood volume, and hemoglobin. During storage, different levels of PGE2, TxB2, IL-1-β, IL-6 for WB, filtered RBC concentrates, and unfiltered RBCs were found. The higher levels of PGE2, TxB2, IL-1-β, and IL-6 were found in the WB and RBC salvaged units than the filtered RBCs or unfiltered RBC units. There was no statistically significant difference between WB and salvaged RBCs. Higher levels of leukocytes and platelets were found in WB units and salvaged RBCs as compared to filtered or unfiltered RBCs. Conclusions: The eicosanoid and cytokine levels in the salvaged, filtered RBC, unfiltered RBC, and WB units stayed within physiological limits, suggesting that these levels do not contribute to the risk of nonhemolytic, immunomodulated transfusion reactions, even in massive transfusions.

Arachidonate 5-lipoxygenase and cyclooxygenase metabolites from guinea pig eosinophils and macrophages.

To investigate the cellular sources of arachidonate metabolites during asthma, in vitro productions of thromboxane (TX) B2, prostaglandin (PG) D2, leukotriene (LT) B4 and cysteinyl (Cys) LTs from guinea pig eosinophils and macrophages simultaneously stimulated with the Ca ionophore A23187 were investigated. Eosinophils produced high levels of LTB4 and TXB2 and relatively low levels of CysLTs and PGD2. Although macrophages released abundant TXB2 and a little PGD2, 5-lipoxygenase metabolites were below detectable levels. In conclusion, eosinophils produced both cyclooxygenase and 5-lipoxygenase metabolites, while arachidonate metabolism in the macrophages was almost completely inclined toward the cyclooxygenase pathway.

Evolution of Streptozotocin–Pancreatic Damage in the Rat: Modulatory Effect of Endothelins on the Nitridergic and Prostanoid Pathway

Many lines of evidence indicate that an increased pancreatic production of nitric oxide (NO) and prostaglandins (PGs) is found in the pancreas of streptozotocin-diabetic rats and that endothelins (ETs) are closely related to the nitridergic and prostanoid pathway in several tissues. In the present study the relationship between NO, ETs, and PGs has been explored in isolated pancreatic tissue from streptozotocin-diabetic rats. Pancreatic ET levels are higher in pancreatic tissues from diabetic (D) rats compared to control (C) animals. The addition of nitric oxide synthase (NOS) inhibitors (1 mM NG-nitro-l-arginine methyl ester, 600 μM NG-monomethyl-l-arginine) in the incubating medium reduces and NO donors (SIN-1, 300 μM spermine supress, NONOate 100 μM) increases ET levels in pancreatic slices from C and D animals. PGE2 (10−7 M) increases and indomethacin (10−6 M) decreases ET pancreatic production only in D but not in C tissues when added into the incubating bath. When tissues are incubated in the presence of endothelin 1 (ET-1) (10−7 M), NOS activity is higher in C pancreas, while the ET-receptor antagonist bosentan (B) decreases NOS levels in D but not in C tissues. When pancreatic arachidonic acid (AA) conversion to prostaglandins was explored, ET-1 increased PGF2α, PGE2, and TXB2 levels in C but not in D tissues. B abolishes TXB2 increment due to the diabetic state, but failed in modulating AA conversion to 6-keto PGF1α, PGF2α and PGE2 in D pancreas. Our results show an alteration in AA metabolism, ET production, and NO increment associated with pancreatic damage due to streptozotocin.

Effects of Dietary ω-3 and ω-6 Lipids and Vitamin E on Serum Cytokines, Lipid Mediators and Anti-DNA Antibodies in a Mouse Model for Rheumatoid Arthritis

Objective: Omega-3 (ω-3) fatty acid rich-fish oil (FO) and vitamin E (vit-E) may delay the progress of certain autoimmune diseases. The present study examined the mechanism of action of ω-3 and ω-6 lipids and vit-E on the serum cytokines and lipid mediators in autoimmune-prone MRL/lpr mice (a model for rheumatoid arthritis, RA). The lpr (lymphoproliferative) gene is overexpressed in these mice causing extensive lymphoproliferation, lupus-like symptoms and accelerated aging.Methods: Weanling female MRL/lpr and congenic control MRL/++ mice were fed 10% corn oil (CO, ω6) or FO-based semipurified diets containing two levels of vitamin E (vit-E-75, I.U. and vit-E-500 I.U./Kg diet) for four months. At the end of the experiment, serum anti-DNA antibodies, cytokines and lipid mediators levels were determined.Results: The appearance of enlarged lymph nodes was delayed in the mice fed FO, and the FO-500 IU vit-E diet offered further protection against enlargement of lymph nodes. The MRL/lpr mice exhibited significantly higher levels of serum anti-dsDNA antibodies. The FO-fed mice had significantly lower serum IL-6, IL-10, IL-12, TNF-α, PGE2, TXB2 and LTB4 levels compared with CO-fed mice. In mice fed 500 IU vit-E diets, the serum IL-6, IL-10, IL-12 and TNF-α levels were significantly lower and serum IL-1β was significantly higher compared to 75 IU-vit-E-fed mice in CO/FO or both. The levels of anti-DNA antibodies, IL-4, IL-6, TNF-α, IL-10 and IL-12 were higher in the sera of MRL/lpr mice. The FO diet lowered the levels of these cytokines (except IL-4) and lipid mediators. Adding 500 IU of vit-E to the FO diet further lowered the levels of IL-6, IL-10, IL-12, and TNF-α.Conclusion: It is clear from our observations that the beneficial effects of FO can be enhanced by the addition of 500 IU of vit-E in the diet. The FO diet containing 500 IU of vit-E may specifically modulate the levels of IL-6, IL-10, IL-12 and TNF-α and thereby may delay the onset of autoimmunity in the MRL/lpr mouse model. The observations from this study may form a basis for selective nutrition intervention based on specific fatty acids and antioxidants in delaying the progress of RA.

THE 5‐HT2 RECEPTOR ANTAGONIST SARPOGRELATE REDUCES URINARY AND PLASMA LEVELS OF THROMBOXANE A2 AND URINARY ALBUMIN EXCRETION IN NON‐INSULIN‐DEPENDENT DIABETES MELLITUS PATIENTS†

1. Therapeutic effects of a 5-HT2 receptor antagonist sarpogrelate on microalbuminuria and thromboxane (TX)A2 biosynthesis were examined in non-insulin-dependent diabetes mellitus (NIDDM) patients. 2. In protocol I, the ankle-brachial pressure index (API; an indicator of peripheral blood flow) and urinary albumin excretion (UalbV; an indicator of renal function) were determined in 42 NIDDM patients who had been treated with 300 mg/day sarpogrelate for 8 weeks. In an analysis of the results, the NIDDM patients were divided into four groups based on the severity of either vasculopathy or nephropathy as follows: group A, API < 0.9, UalbV > or = 100 mg/day; group B, API < 0.9, UalbV < 100 mg/day; group CAPI > or = 0.9, UalbV > or = 100 mg/day; and group D, API > or = 0.9, UalbV < 100 mg/day. 3. In protocol II, 10 NIDDM patients with UalbV values > 100 mg/day were divided into two groups to further confirm the effect of sarpogrelate on albuminuria: group E, the sarpogrelate treatment group (n = 5); and group F, the no treatment group (n = 5). 4. In protocol I, the incidence of a cold sensation in the lower extremities was reduced from 45.2 to 21.4% following sarpogrelate treatment. In patients with UalbV > or = 100 mg/day (groups A and C), UalbV was significantly decreased independent of API, while it did not change in patients with UalbV < 100 mg/day (groups B and D). Plasma TXB2 levels were significantly decreased following sarpogrelate treatment, whereas plasma 6-keto-prostaglandin F1 alpha levels were not. 5. In protocol II, in the sarpogrelate treatment group (group E), albuminuria was significantly improved and both plasma levels TXB2 and urinary TXB2 excretion were significantly decreased. In contrast, in the untreated group (group F), neither plasma levels TXB2 nor urinary TXB2 excretion was changed. 6. In conclusion, microalbuminuria was improved by treatment with the 5-HT2 receptor antagonist sarpogrelate independent of latent vasculopathy. Blockade of 5-HT2 receptors is suggested to be beneficial for the treatment of nephropathy in NIDDM patients. It is possible that the inhibition of TXA2 biosynthesis is involved in the therapeutic effect of 5-HT2 receptor antagonists.

Loop diuretics enhance the secretion of prostacyclin in vitro, in healthy persons, and in patients with chronic heart failure.

Previous studies suggest that the acute haemodynamic effects of loop diuretics are due to a direct dilation of blood vessels and are not related to diuretic properties, but possibly to prostaglandin secretion. We investigated whether in vitro human endothelial and renal epithelial cells responded to torasemide or furosemide with enhanced secretion of the vasodilator prostaglandin prostacyclin (PGI2). We also investigated the effects of loop diuretics on plasma concentrations of PGI2 and its physiological antagonist thromboxane after 25 min of administration of drugs in 44 patients with congestive heart failure (CHF) and 44 healthy volunteers. The PGI2 levels were measured after extraction in ethyl acetate by RIA as levels of 6-KetoPGF1alpha, a stable metabolite from a non-enzymatic degradation. TxB2 concentration, the stable hydrolysis product of TxA2, was also measured by RIA. In human endothelial and renal epithelial cells, both loop diuretics induced an increase of 6-KetoPGF1alpha secretion that reached a peak after about 5 min and remained stable for 30 min of exposure to the drugs. The magnitude of the phenomenon was lesser in epithelial than in endothelial cells. Moreover, in both cell lines, there was a significantly higher secretion of 6-KetoPGF1alpha to torasemide than furosemide (P < 0.05). Concentrations of 6-KetoPGF1alpha at baseline were similar between the groups of CHF patients receiving the two different drugs. After 25 min of both drugs, 6-Keto-PGF1alpha significantly increased (P < 0.01), and this was significantly higher in patients treated with 10 mg of torasemide (P < 0.05 vs furosemide). Levels of PGI2 at baseline were lower in healthy controls than those reached by CHF patients and similar between groups. After 25 min of both drugs, PGI2 plasma levels were significantly increased (P < 0.01). Baseline values of TxB2 were significantly higher in CHF patients compared with controls (P < 0.01 vs respective groups). and, more importantly, furosemide but not torasemide increased TxB2 levels in patients and controls (P < 0.05 vs baseline). Our study is the first demonstration in human tissue of increased secretion of PGI2 both in vitro and in vivo, after torasemide or furosemide administration. This phenomenon, which may explain in part the vasodilatory effects of these drugs, was more evident with torasemide and was reached at lower concentrations of the drug. Accordingly, we also found that furosemide but not torasemide stimulated the release of the PGI2 physiological antagonist thromboxane in CHF patients and healthy controls.

ARE LIPID MEDIATORS IMPLICATED IN THE PRODUCTION OF PRO- AND ANTI-INFLAMMATORY CYTOKINES DURING CARDIOPULMONARY BYPASS GRAFT WITH EXTRACORPOREAL CIRCULATION?

In this study the authors assessed the sequential release of lipid mediators (TXB2, PGE2, 6-keto-PGF1α, LTB4, LTC4, PAF), pro-inflammatory cytokines (IL-6, IL-8, TNF-α) and anti-inflammatory cytokines (IL-4, IL-10) in 17 patients undergoing coronary artery bypass graft (CABG) with extracorporeal circulation (ECC). Time course of appearance of inflammatory mediators revealed the early and transient increase in lipid mediator plasma concentrations (6-keto-PGF1α, LTB4, LTC4, PAF) whereas cytokines (IL-6, IL-8, IL-10) were involved only in late pre- and post-operative periods. No variation of TXB2, PGE2, IL-4 and TNF-α levels were found. No correlation was documented between the levels of lipid mediators and pro- or anti-inflammatory cytokines suggesting that lipidic compounds are not implicated in the genesis of cytokines which appear much later involved. Despite the common use of high doses of aprotinin (a non-specific enzyme inhibitor) in hope to abrogate the inflammatory response to cardiopulmonary bypass procedure, this study reports the persistent release of several inflammatory compounds that might be involved in the post-CABG multiple organ failure syndromes.

Diabetes, Oxidative Stress, and Platelet Activation

Diabetes mellitus is a major source of morbidity in developed countries and, among its comorbid conditions, atherosclerosis is perhaps the most important. Since the availability of insulin, up to three fourths of all deaths among diabetics can be directly attributed to coronary artery disease (CAD).1 In adult patients with diabetes, the risk of CAD is 3- to 5-fold greater in than nondiabetics despite controlling for other known CAD risk factors.1 In patients with IDDM, up to one third will die of CAD by the age of 50 years.2 A number of known risk factors for CAD, such as hypertension, central obesity, and dyslipidemia, are more common in diabetics than in the general population.1 Despite this prevalence of risk factors, no more than 25% of the excess CAD risk in diabetes can be accounted for by known risk factors.2 Thus diabetes represents a major contributing factor to the CAD burden in the developed world, and most of the excess attributed risk of CAD in diabetics cannot be readily quantified with the use of traditional risk factor analysis. Diabetes is associated with a variety of metabolic abnormalities, principle among which is hyperglycemia. The relation between hyperglycemia and CAD is the subject of considerable debate because serum glucose does not consistently predict the existence of CAD.2 Presumably, this confusion stems from the reliance on a single blood glucose measurement, as recent prospective data have clearly established a link between a marker for chronic average glucose levels (HbA1C) and cardiovascular morbidity and mortality.3 There is considerable controversy with respect to the precise mechanism by which hyperglycemia may contribute to the development of CAD in diabetes. Established sequelae of hyperglycemia, such as cytotoxicity, increased extracellular matrix production, and vascular dysfunction, have all been implicated in the pathogenesis …

Effect of oral contraceptives containing 20 and 35 μg ethinyl estradiol on urinary prostacyclin and thromboxane metabolite levels in smokers and nonsmokers

The interaction between smoking and oral contraceptive (OC) use with respect to thrombogenesis was investigated by studying the effects of OC and smoking on urinary prostacyclin (PGI 2) and thromboxane A 2 (TxA 2) metabolite levels in smokers and nonsmokers. Sixty healthy women, aged 19–32 years, who were not taking any hormonal treatment for at least 3 months before initiating the study, were divided into three equal groups: OC users who smoked (N = 20), OC users who did not smoke (N = 20), and a control group of 10 smokers and 10 nonsmokers. Each OC treatment group was randomized to receive either norethindrone (NET) acetate (1 mg)/ethinyl estradiol (EE 2) (35 μg) (N = 10) or NET acetate (1 mg)/EE 2 (20 μg) (N = 10) daily for 3 months. Overnight urine collections and fasting blood samples were obtained at baseline and at the end of the 3-month study. Serum levels of NET and EE 2, as well as urinary levels of cotinine and the stable metabolites of PGI 2 and TxA 2, namely 6-keto-prostaglandin F 1α (6-keto-PGF 1α) and thromboxane (TxB 2), respectively, were measured by specific immunoassays. Analysis of pre- to posttreatment changes in mean urinary 6-keto-PGF 1α and TxB 2 levels for each subgroup, as determined by smoking status and EE 2 dose, showed no statistically significant differences. Also, no significant differences were found in each subgroup with respect to changes in the 6-keto-PGF 1α/TxB 2 ratios. Large intersubject variability in urinary 6-keto-PGF 1α and TxB 2levels were observed in all subgroups. The results of this study indicate that both low-estrogen–dose compounds, when used by smokers or nonsmokers, did not significantly alter the ratio of PGI 2 to TXA 2 metabolites, compared with pretreatment. However, the small number of subjects and the large intersubject variability in this study make it difficult to determine if there is a significant difference between the 20- and 30-μg EE 2 doses.

The effects of a thromboxane A2 synthesis inhibitor and a prostaglandin I2 analogue on experimental acute necrotizing pancreatitis in rats.

To elucidate the role of thromboxane A2 (TxA2) and prostaglandin I2 (PGI2) in acute necrotizing pancreatitis (ANP) in rats and to determine the effect of the TxA2 synthesis inhibitor OKY-046 and the PGI2 analogue OP-2507, the levels of two prostanoids (TxB2, 6-keto PGF1alpha) and two types of phospholipase A2 (PLA2) activity (cytosolic and secretory) were measured in plasma and three tissues (pancreas, lung, and kidney) after injection of a mixed solution of 5% sodium taurocholate and 0.1% trypsin into the pancreatic duct to induce ANP. The survival rate 24 h after inducing ANP was 33.3% in the nontreated group, versus 83.3 and 58.3% in the groups treated with OKY-046 and OP-2507, respectively. Only the group treated with OKY-046 showed significant improvement compared with the nontreated group. The plasma, pancreatic, and pulmonary TxB2 levels decreased significantly in the group treated with OKY-046, and the histopathological changes were not as severe. The levels of pancreatic and pulmonary cytosolic PLA2 activities decreased, and plasma and pancreatic secretory PLA2 activities also decreased. In conclusion, the levels of both types of PLA2 activity and TxA2 production decreased, and the survival rate improved as a result in the group treated with OKY-046, but OP-2507 had no effect on ANP. TxA2 and two types of PLA2 activity play an important role in the process of aggravation of acute pancreatitis.

Urothelial synthesis of prostanoids in the ovine ureter.

The purpose of this study was to investigate the site of production (urothelium/smooth muscle) and quantitative release of prostanoids in the ureter. Quantitative analysis of prostacyclin (PGI2) was by its metabolite, 6-keto PGFalpha, thromboxane (TXB2) and prostaglandin F2alpha. Synthesis by radiometry and radioimmunoassay was performed in vitro in sheep ureter specimens before and after removal of the inner epithelial layer and after addition of indomethacin. The major prostanoids present in the ureter were PGI2 and TXB2; PGI2 was quantitatively the largest component. Removal of the thin inner epithelial layer (urothelium) reduced mostly PGI2; addition of arachidonic acid significantly augmented PGI2 only in ureters with intact urothelium but did not alter TXB2 levels. The main source of prostanoid synthesis (PGI2) of the ureter is to be found in the urothelium. The functional role of the prostanoids may be related to coordination of peristalsis.

Glioma prostaglandin levels correlate with brain edema.

The present study was designed to prospectively investigated the prostaglandin (PG) levels and extent of peritumoral edema in 30 cases of glioma by using methods of radioimmunoassay and imaging. Both TXB2 and 6-keto-PGF1 alpha levels in all glioma groups went up over that in the control group. TXB2 level and ratio of TXB2/6-keto-PGF1 alpha were markedly increased with the extent of tumor malignancy. Water concentration in anaplastic astrocytoma and glioblastoma were significantly elevated. Difference in TXB2 level and TXB2/6-keto-PGF1 alpha ratio among three edema grades were statistically significant. TXB2 level and ratio of TXB2/6-keto-PGF1 alpha were closely correlated with water concentration (r1 = 0.53, r2 = 0.72, P < 0.01). Our findings suggested that the metabolism of PG in glioma were in the state of disorder, and that the imbalance between PGI2 and TXA2 may be one of factors which affect the formation of peritumoral edema.

Thromboxane Production in Human Lung During Cardiopulmonary Bypass: Beneficial Effect of Aspirin?

Background. Increased systemic levels of thromboxane (Tx) during cardiopulmonary bypass (CPB) in humans have been reported. It is not known whether this reflects a general systemic response to the surgical procedure or an increased pulmonary production of Tx in response to ischemia and reperfusion. Methods. Thromboxane B 2 levels were measured in the right atrium and left atrium of 14 patients undergoing coronary artery bypass grafting for angina. Eight patients (group 1) were without aspirin for at least 15 days before operation, and 6 patients (group 2) were treated with aspirin (100 mg/day) for at least 1 month before operation. Levels of TxB 2 were determined by enzyme immunoassay after lipid extraction and separation. Results. Thromboxane B 2 levels were elevated throughout CPB. In group 1, left atrial TxB 2 levels were significantly higher ( p < 0.05) than right atrial levels at all study points during CPB. After pulmonary reperfusion, TxB 2 levels in both atria increased significantly ( p < 0.02) compared with the levels before cross-clamping of the aorta, and there was an increasing gradient between the two atria ( p < 0.05). Mean plasma TxB 2 levels during CPB in group 2 were significantly reduced ( p < 0.0001) in the right atrium (by 73%) and in the left atrium (by 69%) compared with levels in group 1. Conclusions. The rise in TxB 2 levels in the left atrium after CPB in humans reflects production of Tx mainly in the lungs, most probably by ischemic pulmonary tissue and intravascular hematologic components. Aspirin markedly reduces Tx production during CPB, and it might play a major role in preventing pulmonary injury after operations with CPB in humans.

Selective inhibition of cyclooxygenase-2 by NS-398 in endotoxin shock rats in vivo.

The role of cyclooxygenase (COX)-2 was examined using a rat endotoxin shock model and the potency and selectivity of NS-398, a COX-2 selective inhibitor in vitro, for COX-2 activity was examined in vivo. Male Wistar rats (weighing 140-180 g) were used. Lipopolysaccharide (LPS, 1 mg/kg, i.v.) was administered to rats (LPS-treated rats) and expression of COX-1 mRNA and COX-2 mRNA in the aorta and peripheral blood leukocytes was examined by RT-PCR. COX activity was assessed by measuring the plasma 6-keto prostaglandin (PG) F1 alpha, PGE2 and thromboxane (TX)B2 30s after administration of arachidonic acid (AA, 3 mg/kg, i.v.), NS-398 (0.3-100 mg/kg, p.o.) or indomethacin (0.3-3 mg/kg, p.o.) was administered 1 h before the AA injection. COX-2 mRNA was detectable in the aorta and peripheral blood leukocytes at least from 3 to 9 h after the LPS injection but not in non-LPS-treated rats. Plasma 6-keto PGF1 alpha, PGE2 and TXB2 levels after AA injection into LPS-treated rats were significantly enhanced compared to findings in non-LPS-treated rats. NS-398 showed significant inhibition of the increase in PGs in LPS-treated rats, the ED50 values being 0.35 mg/kg for 6-keto PGF1 alpha, 1.5 mg/kg for PGE2 and < 0.3 mg/kg for TXB2. NS-398 even at 100 mg/kg did not significantly suppress the increased PGs levels in non-LPS-treated rats. In contrast, indomethacin significantly inhibited plasma PGs levels after AA injection into LPS-treated rats and non-LPS-treated rats. The ED50 values in LPS-treated rats, determined by 6-keto PGF1 alpha, PGE2 and TXB2 production, were 1.0, 1.3 and 2.3 mg/kg and those in non-LPS-treated rats were 0.42, 0.24 and 0.93 mg/kg, respectively. In a rat endotoxin shock model, expression of COX-2 plays a role in an increase in COX activity. NS-398 showed preferential inhibitory effects on COX-2 activity in vivo. This approach is useful to directly analyze the inhibitory activity of NSAIDs for COX-1 and COX-2 in vivo.

PAF modulates eicosanoids and TNF release in immune-complex arthritis in rats

The participation of lipid mediators and tumor necrosis factor (TNF) on an experimental model of immune-complex arthritis was investigated. Male Wistar rats received intraarticular injection of rabbit antibodies to bovine serum albumin into the knee joint followed by i.v. injection of the antigen. The levels of eicosanoids and TNF released into the synovial exudates were then assessed using ELISA and the L929 lytic cell assay, respectively. Increase in the levels of LTB4, TXB2 and PGE2 were detected 5 min, 5 min, and 6 h after arthritis induction, respectively. Pretreatment with the PAF receptor antagonist WEB 2170 decreased the levels of PGE2 and increased those of LTB4, without altering TXB2 levels. Increase in the levels of TNF was detected at 3 h of arthritis. Pretreatment with either the cycloxygenase inhibitor indomethacin or the 5-lipoxygenase inhibitor L-663,536 had no effect on TNF levels. Pretreatment with WEB 2170 significantly decreased TNF levels. These results are the first demonstration of eicosanoids and TNF release in immune-complex arthritis. The data also suggest that PAF had both a positive and negative modulatory role on the release of PGE2 and LTB4, respectively. Moreover, TNF release into the synovial exudate did not depend on eicosanoids whereas platelet activating factor (PAF) appeared to mediate the release of this cytokine in the model.

8-Epi-PGF2alpha induces airflow obstruction and airway plasma exudation in vivo.

8-Epi-prostaglandin F2alpha (8-epi-PGF2alpha) is an F2-isoprostane formed mainly via noncyclooxygenase pathways in vivo. We investigated whether 8-epi-PGF2alpha has any effect on airflow obstruction and plasma exudation in vivo. Airflow obstruction was quantified by measuring lung resistance (RL) in anesthetized and ventilated guinea pigs, and plasma exudation was quantified by the Evans Blue dye method (20 mg/kg intravenously). Intratracheal instillation of 8-epi-PGF2alpha (1 nmol or 10 nmol) caused dose-related increases in RL. Furthermore, the higher dose of 8-epi-PGF2alpha produced Evans Blue dye extravasation in main bronchi and intrapulmonary airways. A prostanoid TP-receptor antagonist, BAY u3405 (1 mg/kg intravenously), abolished the airway effects of 8-epi-PGF2alpha (10 nmol). A thromboxane A2 (TxA2) synthase inhibitor, OKY-406 (30 mg/kg intravenously), significantly attenuated these effects of 8-epi-PGF2alpha (10 nmol). The level of TxB2, a stable TxA2 metabolite, increased in bronchoalveolar lavage fluid (BALF) after 8-epi-PGF2alpha instillation. We conclude that 8-epi-PGF2alpha causes airflow obstruction and plasma exudation in vivo. This effect may be mediated primarily via prostanoid TP-receptors, and a secondary generation of TxA2 may be involved in part of the airway responses in 8-epi-PGF2alpha in the guinea pig.

Clinical Potential of Anti-Thromboxane A2 Agents in Bronchial Asthma

Animal and human studies have shown that various kinds of chemical mediators may participate in the pathogenesis of bronchial asthma. Among these mediators, thromboxane A2 (TXA2) is recognised as important in bronchial responses and the pathogenesis of airway hyperresponsiveness. The reasons are as follows. (i) TXA2 (or mimetics) is a powerful constrictor of bronchial muscle in vitro and in vivo. (ii) Levels of TXB2, a metabolite of TXA2, increase in blood or bronchoalveolar lavage fluid after allergen challenge in atopic asthmatic patients. (iii) TXA2 mimetics induce airway hyperresponsiveness to nonspecific stimuli such as acetylcholine or methacholine. (iv) TXA2 synthetase inhibitors or TXA2 receptor antagonists inhibit asthmatic responses or airway hyperresponsiveness in various animal models and in patients with asthma.