Increase In Thromboxane B2 Research Articles

Plasma Levels of Eicosanoids after Transfusion of Intraoperatively Salvaged Blood

Background: The interest in autologous red blood cell salvage is increasing rapidly, but it is well known that platelets and white cells are activated during cell washing. Therefore, we aimed to determine whether or not eicosanoids transfused together with the salvaged blood are responsible for nonhemolytic immunological transfusion reactions. Materials and Methods: In 11 patients who underwent radical prostatectomy we studied the release of eicosanoids, prostaglandin E2 (PGE2) and thromboxane B2 (TxB2), in association with reinfusion of intraoperatively salvaged blood. Blood samples were taken before operation, on days 1 and 3 after operation and before and after cell washing. Results: There was a twofold increase in PGE2 and a twentyfold increase in TxB2 in the unwashed salvaged blood. Washing caused a reduction in eicosanoid plasma levels of up to 95%, but a significantly lower level in relation to its corresponding preoperative value was only found for PGE2. After transfusion of an average of 420 ml RBC sediment from washed blood, the patients' plasma concentrations of PGE2 and TxB2 on the 1st and 3rd postoperative day did not significantly differ compared to baseline values. Conclusion: Our data support the notion that RBC sediment from ‘salvaged’ and washed autologous blood contains increased amounts of PGE2 and TxB2. It remains, however, questionable if these passively infused eicosanoids become biologically active. According to our study, the PGE2 and TxB2 transfused are apparently not responsible for nonhemolytic immunological transfusion reactions.

Effects of picotamide on release of endothelin-1, thromboxane and prostacycline after treadmill stress in patients with peripheral artery disease.

To assess the effects of picotamide, an antithromboxane receptor and antithromboxane synthase drug, on vascular function and endothelin-1 release, 20 patients with peripheral arterial disease, without hypertension or diabetes mellitus, receiving placebo and picotamide (900 mg/day) were studied. The modifications of vascular parameters were evaluated by arterial distensibility index and postischemic hyperemia test (postischemic perfusion index and recovery time). Endothelin-1, prostacycline, and thromboxane B2 were determined under resting conditions and after treadmill test. Picotamide treatment caused a decrease of resting thromboxane B2 and endothelin-1 concentrations, produced an improvement of the vascular function as seen by the increase of vascular parameters reported, and attenuated the ischemic treadmill-induced increase of thromboxane B2, but not of endothelin-1. These data confirm that the picotamide improved vascular flow by the reduction of thromboxane-mediated effects, reduced resting endothelin-1 levels, but did not attenuate endothelin-1 concentrations induced by the treadmill stress.

The effects of hyperoxia on the biosynthesis of cyclooxygenase products and haemodynamic response to nitric oxide synthase inhibition with L-NAME in endotoxaemic pigs.

The interaction between constitutive nitric oxide and oxygen may depend on the degree of tissue oxygenation and may play a critical role in the pathophysiological response to endotoxaemia. We investigated if hyperoxia (100% O2) attenuated the systemic and pulmonary vasoconstriction and increased biosynthesis of thromboxane B2 (TXB2) and 6-keto-prostaglandin (PG) F1alpha induced by inhibition of nitric oxide synthase with NG-nitro-L-arginine-methyl-ester (L-NAME) in a porcine model of endotoxaemia. Twenty-two domestic, random source pigs, weighing 15.4 +/- 2.7 kg (mean +/- standard deviation) were the subjects of this study. Pigs were anaesthetized with isoflurane in 100% O2, orotracheally intubated and ventilated to maintain normocapnia, and then instrumented for haemodynamic monitoring. Following instrumentation, pigs were maintained at an end-tidal isoflurane concentration of 2%. Pigs were randomly assigned to treatment groups: saline + 30% O2 (Control, n = 6); Escherichia coli lipopolysaccharide (5 microg/kg/h from 1 to 2 h followed by 2 microg/kg/h from 2 to 5 h) + 30% O2 (LPS, n = 4); L-NAME (0.5 mg/kg/h, from 0 to 5 h) + LPS + 100% O2 (n = 6); and L-NAME + LPS + 30% O2 (n = 6). L-NAME and endotoxin significantly (P < 0.05) increased mean arterial pressure, mean pulmonary arterial pressure, and systemic and pulmonary vascular resistance index beginning at 90 min. When results were pooled across all time periods, mean arterial pressure and mean pulmonary arterial pressure were significantly higher in the L-NAME + LPS + 30% O2 group than all other groups, reflecting pulmonary and systemic vasoconstriction. Hyperoxia attenuated the L-NAME + LPS-induced increases in TXB2 and 6-keto-PGF1alpha concentrations at 90 and 120 min and 120 min, respectively, although the differences were not statistically significant. These results support the observation that nitric oxide synthase inhibition with L-NAME has deleterious haemodynamic effects in this model of endotoxaemia. The temporal attenuation of L-NAME-induced pulmonary and systemic vasoconstriction by hyperoxia suggested that the haemodynamic effects of acute endotoxaemia were in part influenced by the relative amounts of nitric oxide and oxygen present.

Effect of Post-Treatment with Granulocyte Colony-Stimulating Factor on Endotoxin-Induced Lung Injury in Sheep

We administered a bolus of G-CSF (250 μg/body) just after the infusion of endotoxin (1 μg/kg) in awake sheep with chronic lung lymph fistula to examine the effect of post-treatment with G-CSF on endotoxin-induced lung injury. We measured pulmonary hemodynamics, lung lymph flow, and concentrations of thromboxane B2 and 6-keto-prostaglandin Flα in plasma and lung lymph. In the G-CSF post-treated group, the pulmonary arterial pressure, pulmonary vascular resistance, and lung lymph flow did not significantly increase in the late period (3–5 h after endotoxin infusion). The arterial oxygen gas tension in the late period was higher in the G-CSF post-treated sheep than in those that received only endotoxin. Although the level of thromboxane B2 in plasma significantly increased at 1h after endotoxin, the lung lymph flow did not increase much in the G-CSF post-treated group. We conclude that post-treatment with G-CSF instead attenuates the degree of pulmonary vascular leakage on endotoxin-induced lung injury and increased thromboxane B2, the principle metabolite of thromboxane A2, may not exacerbate the injury in awake sheep.

Involvement of phospholipase A2 in gentamicin-induced rat mesangial cell activation.

The role of the phospholipase A2 (PLA2) activation in the gentamicin (Gent)-induced rat mesangial cell activation has been studied. Gent (10(-5) M) induced a time-dependent mesangial planar cell surface area reduction that was significantly inhibited by the PLA2 inhibitors aristolochic acid (AA) and quinacrine, by the platelet-activating factor (PAF) blocker BN-52021 (BN), and by verapamil. These substances also inhibited Gent-induced [3H]thymidine incorporation into DNA (AA, 504 +/- 20; quinacrine, 555 +/- 66; BN, 1,126 +/- 120; and verapamil, 896 +/- 109; vs. 1,818 +/- 35 cpm/well in cells treated with Gent alone) and the Gent-induced increase in cell number (AA, 20,116 +/- 2,696; quinacrine, 24,687 +/- 1,481; BN, 26,122 +/- 1,016; and verapamil, 27,566 +/- 1,214; vs. 47,486 +/- 1,124 cells/well in cells treated with Gent alone). Gent induced a twofold increase in [3H]acetate incorporation into PAF (27 +/- 3 vs. 12 +/- 2 cpm/microgram protein in control conditions) that was completely blocked by AA, BN, or verapamil. Gent increased thromboxane B2 and prostaglandin E2 (PGE2) production, with both increases inhibited by either AA or verapamil. BN only inhibited the Gent-induced mesangial PGE2 production. In addition, Gent increased PLA2 activity (measured as [3H]arachiodonic acid release, 29,849 +/- 2,151 vs. 20,104 +/- 2,308 cpm/well in basal conditions), an effect that was blocked by AA (11,804 +/- 684 cpm/well). These data suggest a major role for PLA2 activation in Gent-induced mesangial cell contraction, proliferation and prostanoid secretion.

Ulinastatin, a human trypsin inhibitor, inhibits endotoxin-induced thromboxane B2 production in human monocytes.

Ulinastatin has an inhibitory effect on certain cytokines produced from lipopolysaccharide (endotoxin)-stimulated human monocytes. However, the effects of ulinastatin on arachidonic acid metabolism in monocytes have not been determined. This study examined the effects of ulinastatin on the arachidonic acid metabolite, thromboxane B2, in response to endotoxin-, phorbol 12-myristate 13-acetate-, or arachidonic acid-stimulated human peripheral blood monocytes. Controlled, human laboratory investigation of monocyte function in vitro. Research facility of a health science university. Five normal volunteers. Mononuclear cells were separated from blood using Histopaque. Monocytes were stimulated with endotoxin (0.1 to 10 micrograms/mL) or other stimulatory agents, which were added simultaneously with or without ulinastatin (25 to 1000 U/mL). None of the compounds in this study altered the cell viability of adherent cellular protein content. Ulinastatin alone did not affect basal thromboxane B2. Endotoxin induced dose-dependent increases in thromboxane B2 production by the monocytes. Ulinastatin (100 U/mL) maximally decreased endotoxin (1.0 microgram/mL)-stimulated thromboxane B2 production, which was not further suppressed with higher ulinastatin concentrations. Increases in thromboxane B2, stimulated by phorbol myristic acid (10 nM) or arachidonic acid (16 microM), were also suppressed by ulinastatin at 100 to 1000 U/mL. These results indicate that ulinastatin may nonspecifically but moderately down-regulate stimulated arachidonic acid metabolism in human monocytes. Therefore, the present results warrant further clinical studies to examine the beneficial effects of ulinastatin in the treatment of patients with sepsis syndrome.

Endothelin-1-induced release of thromboxane A2 increases the vasoconstrictor effect of endothelin-1 in postischemic reperfused rat hearts.

The release and vasoconstrictor effect of endothelin-1 (ET-1) are increased after myocardial ischemia, suggesting a role for ET-1 in ischemia/reperfusion injury. However, the mechanisms of the increased vasoconstriction by ET-1 are unknown. The aim of this study was to test whether ET-1-induced release of thromboxane A2 (TXA2) contributes to the vasoconstrictor effect of ET-1 in nonischemic hearts and whether such release can increase the vasoconstrictor effect of ET-1 in postischemic reperfused hearts. ET-1-induced release of TXA2 was assessed by measurement of the concentrations of its stable metabolite thromboxane B2 (TXB2) in the coronary effluent of nonischemic and reperfused isolated rat hearts before and after administration of 0.01 nmol ET-1 using an enzyme immunoassay. The contribution of ET-1-induced release of TXA2 to the vasoconstrictor effect of ET-1 was assessed by measurement of the effects of ET-1 with and without the cyclooxygenase inhibitor indomethacin or the TXA2/endoperoxide receptor antagonist SQ 30,741 using 31P magnetic resonance spectroscopy. In nonischemic hearts, ET-1 led to a small increase in TXB2 in the coronary effluent (3.9 +/- 1.5 pg/mL; n = 3), but neither indomethacin nor SQ 30,741 significantly diminished the vasoconstrictor effects of ET-1 (reduction of coronary flow, 4.0 +/- 0.4 and 4.5 +/- 0.3 mL/min, respectively, versus 4.9 +/- 0.5 mL/min for ET-1 alone; n = 8, 6, and 9, respectively). In postischemic reperfused hearts, however, ET-1 led to a greater increase in TXB2 (13.7 +/- 1.5 pg/mL; P < .05 versus nonischemic hearts; n = 3), and both indomethacin and SQ 30,741 diminished the vasoconstrictor effects of ET-1 (reduction of coronary flow, 2.6 +/- 0.3 and 2.2 +/- 0.3 mL/min, respectively, versus 4.0 +/- 0.1 mL/min for ET-1 alone; n = 8, 8, and 6, respectively; P < .05). Furthermore, indomethacin and SQ 30,741 prevented the detrimental effects of ET-1 on left ventricular developed pressure, intracellular pH, and phosphocreatine during reperfusion. ET-1-induced release of TXA2 does not significantly contribute to the vasoconstrictor effect of ET-1 in nonischemic hearts but can increase the vasoconstrictor effect of ET-1 in postischemic reperfused hearts.

The effect of 1 ppm nitrogen dioxide on bronchoalveolar lavage cells and inflammatory mediators in normal and asthmatic subjects

Several studies have suggested that patients with bronchial asthma are more susceptible to the potential effects of nitrogen dioxide (NO2) than healthy subjects, with respect to airway responsiveness and lung function. We investigated whether these differences are paralleled by differences in the cellular and biochemical response within the airway lumen. Twelve subjects with mild extrinsic asthma and eight normal subjects breathed either filtered air or 1 ppm NO2 in a single-blind manner during intermittent exercise for 3 h. Bronchoscopy with bronchoalveolar lavage (BAL) was performed one hour after each exposure, and on a third day without exposure (baseline day). Prostanoids, leukotrienes and histamine were analysed in BAL fluid, and the cellular composition of BAL fluid was assessed. In the asthmatic subjects, NO2 induced a small mean drop in forced expiratory volume in one second (FEV1). Differential cell counts in BAL fluid did not reveal significant effects of NO2. Levels of 6-keto-prostaglandin1 alpha (6-keto-PGF1 alpha) were decreased, and levels of thromboxane B2 (TxB2) and prostaglandin D2 (PGD2) in BAL fluid were increased after NO2 compared to filtered air exposure; whereas, prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), histamine and leukotriene levels did not change significantly. The normal subjects showed no change in lung function parameters and a small increase in TxB2 after breathing NO2. We conclude that in subjects with mild asthma NO2 is capable of inducing an activation of cells, which is compatible with enhancement of airway inflammation, even if lung function parameters and cellular composition of BAL fluid are not markedly affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined effects of age and exercise on thromboxane B2 and platelet activation

Nine healthy young (27.8 +/- 0.8 yr old, YM) and nine healthy older men (55.4 +/- 1.3 yr old, OM) ran on a treadmill at 70-75% of maximal O2 consumption for 30 min to determine the combined effects of age and acute exercise on plasma thromboxane B2 (TxB2) and beta-thromboglobulin (beta-TG). Blood samples (10 ml) were collected in tubes containing 0.5 ml of 4.5 mM EDTA, 30 mM acetylsalicylic acid, and 1 microM prostaglandin E1 after 15 min of rest, immediately after exercise, and at 30 min of recovery. Concentrations of TxB2 and beta-TG were determined by radioimmunoassay. Samples were adjusted for hemoconcentration and changes in platelet count not accounted for by plasma volume shifts. Data were analyzed with repeated-measures analysis of variance and Tukey's post hoc technique. Resting TxB2 was 53.3 +/- 9.6 and 79.0 +/- 18.2 pg/ml for the YM and OM, respectively. beta-TG at rest was 152.5 +/- 13.9 and 114.0 +/- 10.9 ng/ml for the YM and OM, respectively. No significant age group or exercise-induced differences for TxB2 or beta-TG were found immediately after exercise. TxB2 in the OM (101.7 +/- 16.4 pg/ml) 30 min after exercise was significantly (P = 0.05) higher than that in the YM (54.4 +/- 6.2 pg/ml). beta-TG values 30 min after exercise were not significantly different: 183.3 +/- 26.9 and 169.9 +/- 17.0 ng/ml in the OM and YM, respectively. These data suggest that OM may experience greater increases in TxB2 than YM 30 min after exercise and may be more predisposed to platelet activation.

EFFECT OF A PLATELET-ACTIVATING FACTOR ANTAGONIST AND DESFERRIOXAMINE ADMINISTRATION ON EICOSANOID PRODUCTION IN RAT PANCREAS TRANSPLANTATION

Eicosanoid metabolism and its relationship with platelet-activating factor and oxygen free radical production in rat pancreas transplantation has been studied herein. Male Sprague-Dawley rats were classified in 4 experimental groups (n = 8 each) as follows: group 1, control; group 2, pancreas transplantation, after 12 hr of organ preservation in University of Wisconsin solution; group 3, same as group 2 with desferrioxamine administration before revascularization of the organ in the recipient rat; and group 4, same as group 3 with administration of a platelet-activating factor antagonist (BN-52021). The results show post-transplantation increases in eicosanoid production in pancreatic tissue. The fact that desferrioxamine and BN-52021 administration could reverse increases in thromboxane B2, leukotriene B4, and 12-hydroxyeicosatetraenoic acid but only BN-52021 affected 6-keto-PGF1 alpha levels suggests the existence of a close relationship between platelet-activating factor and oxygen free radical in eicosanoid production in pancreas transplantation and it points to a differential role of metabolites produced by circulatory cells and endothelial cells.

Platelet Activation Induced by lnterleukin-6: Evidence for a Mechanism Involving Arachidonic Acid Metabolism

The effect of IL-6 on in vitro platelet function was investigated. Platelet-rich plasma (PRP) incubated with IL-6 showed a dose dependent enhancement of agonist induced maximum aggregation (AIMA) and secretion of thromboxane B2 (TXB2) as measured by RIA, in short term incubations. Dazoxiben (0.2 to 160 microM) pretreated PRP incubated with IL-6 and aggregated with ionophore A23187, showed a dose dependent inhibition of TXB2 secretion concomitant with a dose dependent abrogation of IL-6's enhancement of AIMA. A similar abrogation of AIMA was observed when these experiments were repeated using indomethacin. Further, PRP incubated with IL-6 showed a dose dependent increase in TXB2 and BTG secretion as measured by RIA and an increased incorporation of actin binding protein, talin, and myosin into the cytoskeletal core (triton insoluble residue) as shown by SDS-PAGE. The integrin glycoprotein IIIa (GPIIIa) was also observed to be retained into the cytoskeleton by immunoblot. These results suggest that IL-6 activates platelets in vitro and enhances AIMA via a mechanism involving arachidonic acid metabolism.

Increased graft survival by utilization of 15-deoxyspergualin in a canine pancreatic allotransplantation model.

The purpose of this study was to evaluate the effectiveness of 15-deoxyspergualin (DSG) administration against acute rejection of canine pancreatic allografts. Subsequent to partial pancreatic allotransplantation and total extirpation of the pancreas, 20 adult mongrel dogs were divided into four groups and treated with saline (group 1, controls, n = 5), DSG at 1.0 mg/kg/day (group 2, n = 5), DSG at 3.0 mg/kg/day (group 3, n = 5), or DSG at 5.0 mg/kg/day (group 4, n = 5) on postoperative days 4-7. The graft survival, defined by a fasting serum glucose level < 150 mg/dl, was significantly prolonged from 6.2 +/- 1.2 days in group 1 to 12.4 +/- 2.7 days in group 3 (p < 0.05) and to 16.8 +/- 3.2 days in group 4 (p < 0.05). Graft survival was not significantly prolonged in group 2, however. Two normoglycemic dogs in group 4 died due to gastrointestinal toxicity, one of the most serious side effects of DSG. The observation that the serum insulin levels increased in dogs treated with DSG was compatible with dose-dependent graft survival and suggested that DSG had no toxic effects on pancreatic endocrine function. In group 1 significantly increased thromboxane B2 (TXB2) levels and TXB2/6-keto-prostaglandin F1 alpha (PGF1 alpha) ratios were observed on postoperative days 3-5 which was thought to reflect acute rejection. Following administration of DSG, both TXB2 levels and TXB2/PGF1 alpha ratios were decreased on the 5th postoperative day in groups 2-4.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of two magainin peptides on eicosanoid release from rat peritoneal macrophages.

Magainins are novel polycationic peptides with broad-spectrum antimicrobial activity, including activity against gram-negative bacteria. Gram-negative bacteremia can elicit endotoxic shock that is associated with the increased formation of eicosanoids. Inhibition of eicosanoid synthesis has been shown to improve the outcome of experimental endotoxic shock. The aim of the present study was to test the in vitro effects of two magainin peptides, MSI-97 (M1) and MSI-98 (M2), on eicosanoid synthesis by rat peritoneal macrophages (M phi) stimulated by Salmonella enteritidis lipopolysaccharide (LPS; 50 micrograms/ml) and Salmonella minnesota lipid A (5 micrograms/ml) and to compare their effects on LPS reactivity with a metachromatic dye. M1 (100 micrograms/ml) significantly (P < 0.05) reduced LPS-stimulated synthesis of thromboxane B2 (TXB2), without changing 6-keto-prostaglandin F1 alpha in M phi. Similarly, M2 (10 micrograms/ml) significantly attenuated M phi synthesis of TXB2 stimulated by either LPS or lipid A. However, at a higher concentration (100 micrograms/ml), M2 but not M1 significantly augmented LPS-induced increases in TXB2 and 6-keto-prostaglandin F1 alpha. Polymyxin B (40 micrograms/ml) inhibited LPS production and lipid A-stimulated TXB2 production. M1 (100 micrograms/ml) and polymyxin B (10 and 40 micrograms/ml) also inhibited calcium ionophore A23187 (10 microM)-induced synthesis of TXB2. The lipid A moiety of LPS reacts with dimethylmethylene blue dye, providing a metachromatic assay of LPS. This metachromatic reaction with lipid A was significantly reduced by polymyxin B and M2 at all concentrations. M1 was effective only at the highest M1:lipid A concentration ratio (2:1). Thus, M1 and M2 share some similarities with polymyxin B in inhibiting lipid A reactivity with the dye, which suggests that these magainins may also bind to lipid A. However, M1 was devoid of any inhibitory effects on dye reactivity with S. enteritidis LPS and M2 was inhibitory at only one concentration ratio (1:5). In conclusion, the varied effects of the magainin peptides on LPS, lipid A, and M phi eicosanoid synthesis appear to depend on the type of peptide used and on its concentration.

Protection against platelet-activating factor-induced injury by interferon inducer in perfused rabbit lung.

Platelet-activating factor (PAF) and the interferons (IFN) are released during sepsis and the adult respiratory distress syndrome. The proinflammatory nature of PAF and anti-inflammatory property of IFN led us to investigate interactions between these two mediators in an isolated perfused lung (IPL) preparation. In the IPL, mean pulmonary arterial pressure (Ppa), lung weight gain, and peak airway pressure (Paw) were monitored continuously for 1 h in six groups of rabbits: 1) control, 2) the IFN-alpha/beta inducer polyinosinic:cytidylic acid (polyI:C) alone, 3) PAF alone, 4) polyI:C + PAF, 5) indomethacin + PAF, and 6) AA861 (a 5-lipoxygenase inhibitor) + PAF. At the end of 1 h, microvascular pressure was determined by double-occlusion technique and partition of total pulmonary vascular resistance (RT) was calculated. Serial eicosanoid concentrations in the perfusate also were measured. PAF increased Ppa, Paw, lung weight gain, and RT. These changes were associated with increased thromboxane B2 and decreased leukotriene production. PolyI:C, which induced high levels of serum IFN in rabbits, blocked the PAF-induced increase in Ppa, Paw, lung weight gain, and RT, similar to indomethacin and AA861. PolyI:C suppressed PAF-stimulated release of thromboxane B2 and increased leukotriene levels in the perfusate. The PAF-induced lung responses also were attenuated by pretreatment with human recombinant IFN. These data indicate that polyI:C protects against PAF-induced responses in the rabbit IPL, most likely via its induction of IFN. This effect is related in part to inhibition of thromboxane A2 production stimulated by PAF and leukotrienes.

Mediators of complement-independent granulocyte activation during haemodialysis: role of calcium, prostaglandins and leukotrienes

Granulocyte activation during haemodialysis using cuprophane membrane is mediated by complement-derived anaphylatoxins C3a and C5a. However, neutrophil degranulation induced by modified cellulosic membranes or synthetic membranes does not correlate with C3a or C5a concentrations. Incubation and recirculation experiments were performed to find out which messengers trigger neutrophil degranulation during blood contact with different membrane materials. During in vitro haemodialysis for 2 hours, PMMA and cuprophane induced pronounced degranulation of neutrophils. With PMMA this was associated with increased thromboxane B2 but low C3a levels, while with cuprophane membrane, marked complement activation but only little thromboxane B2 release was observed. Indomethacin (10 microM) nullified all thromboxane B2 response but could not influence elastase release, indicating that cyclo-oxygenase products are not involved in neutrophil degranulation under these conditions. During incubation of blood with dialysis membranes, inhibition of lipoxygenase by esculetin or of phospholipase A2 by hydrocortisone also had no effect on neutrophil degranulation. One messenger involved in granulocyte activation might be free cytosolic calcium. Application of different calcium channel blockers (verapamil, diltiazem, or nitrendipine) did not influence neutrophil degranulation in incubation experiments, in PMMA or cuprophane membranes. In contrast, chelation of plasmatic calcium by sodium citrate or EDTA blunted elastase release induced by these membranes. This study indicates that calcium is a key mediator required for neutrophil degranulation in complement-activating and non-complement-activating dialysis membranes, while activation of the prostaglandin or leukotriene cascade are not required.

Regulation of cyclooxygenase and thromboxane synthase in human monocytes.

Stimulation of human monocytes by lipopolysaccharide or phorbol ester resulted in an increase in thromboxane-B2 and prostaglandin-E2 production, whereas interleukin 1, tumour necrosis factor alpha and leukotriene C4 exerted no effects. Inhibitors of protein kinase C suppressed these increases. The activity of cyclooxygenase was induced 3.2-fold by an 8-h stimulation, whereas thromboxane-synthase and prostaglandin-E-isomerase activities remained unchanged. A glucocorticoid, dexamethasone, blocked both basal and induced prostanoid release, as well as cyclooxygenase activity. By immunoprecipitation, we were able to demonstrate an enhanced de novo synthesis of cyclooxygenase protein induced by lipopolysaccharide and phorbol ester. Dexamethasone suppressed cyclooxygenase synthesis, whereas thromboxane synthase was induced. For cyclooxygenase, we calculated a half-life of 3.2 h in human monocytes, and for thromboxane synthase, a half-life of 28 h. These results suggest that the regulation of differential prostanoid production mainly occurs by up and down regulation of cyclooxygenase.

The effects of testosterone on lipids and eicosanoids in cynomolgus monkeys

The effect of testosterone administration on plasma lipoproteins and eicosanoids was studied in 24 male cynomolgus monkeys. We hypothesized that elevated plasma testosterone would unfavorably alter plasma lipids as well as thromboxane A2 (TxA2) and prostacyclin (PGI2), two eicosanoids that have been linked to the increased incidence of atherosclerosis, myocardial ischemia, and thrombosis. To test our hypothesis, half of the monkeys (N = 12) were subjected to 10 wk of testosterone treatment, whereas the remaining monkeys (N = 12) received a sesame oil vehicle. The plasma concentrations of thromboxane B2 (TxB2) and 6-keto-PGF1 alpha, the stable metabolites of TxA2 and PGI2, respectively, were determined. Additionally, assays were conducted on total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), and triglycerides (TG). Distribution of the HDL subfraction protein was measured by gradient gel electrophoresis. All monkeys exhibited significant increases in TC (P less than 0.001) and low density lipoprotein cholesterol (LDL-C) (P less than 0.001); however, monkeys who received testosterone also displayed significant increases in TxB2 (P less than 0.03) and decreases in HDL-C (P less than 0.03) compared with control monkeys. There was a trend in the HDL-C subfraction data, indicating that testosterone treatment may be associated with a decrease in the larger HDL2b subfraction and a corresponding increase in HDL3c. These results demonstrate that exogenous testosterone adversely alters cardiovascular risk profiles by increasing TXB2 production and decreasing HDL-C. Athletes who use testosterone as an anabolic androgenic steroid may have an increased risk for coronary heart disease.

Stress and fatty liver — Possible indications for dietary long-chain n-3 fatty acids

The favourable effects of eicosapentaenoic acid (EPA)- and doco-sahexaenoic acid (DHA)-rich diets (marine fish, fish oil) on several risk factors for cardiovascular disease are well established. The present survey describes possible new indications for diets supplemented with long-chain n-3 fatty acids. During a standardized psychophysiological stress test (arithmetic, sentence completion tasks) systolic blood pressure after 2 weeks of diets supplemented with either 60 ml/day of sunflower or linseed oil was significantly decreased. During the sunflower oil-rich diet 45 g/day of linoleic acid (LA) and during the linseed oil-rich period 38 g/day of alpha-linolenic acid (LNA) were ingested. After a 2-week diet supplemented with mackerel (2 cans/day equivalent to 2.2 g/day of EPA and 2.8 g/day of DHA) systolic and diastolic blood pressure within the same test design appeared significantly lower. After a herring diet providing 2 cans/day, equivalent to 1.0 g of EPA and 1.8 g of DHA, the blood pressure-lowering effect was minor. The increase of thromboxane B2 (TxB2) during the stress test failed to occur after the fish diets. The results suggest a stress-protective effect of polyenoic acid-rich diets, which appears most pronounced and dose-related after long-chain n-3 fatty acids. In human liver an increase of fat droplet size in hepatocytes is associated with a decrease of the percentage of EPA in liver triglycerides. A diminution of plasma free fatty acids (FFA) after a mackerel diet might contribute to a depressed synthesis of liver triglycerides.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of leukocytes in metabolic and functional derangements of experimental glomerulonephritis

Nephrotoxic nephritis (NTN) is characterized by an influx of leukocytes into the glomerulus, with accompanying glomerular dysfunction and a marked increase in glomerular eicosanoid production. We examined the relationship between the glomerular inflammatory cell infiltrate and the concomitant metabolic/functional changes in this model of renal disease using a combination of in vivo immunologic strategies to both decrease [X-irradiation and cobra venom factor (CVF)] and increase (preimmunization with rabbit immunoglobulin G or accelerated NTN) the inflammatory cell infiltrate. With the use of these manipulations, a close correlation between glomerular leukocytes and the proteinuria of NTN was observed. The ablative strategies (X-irradiation and CVF) also attenuated the increase in leukotriene B4 (LTB4) generation seen with NTN and virtually completely prevented the increase in thromboxane B2 (TxB2) production (basal and angiotensin II elicited). Accelerated NTN, in contrast, increased and prolonged the rise in glomerular LTB4 production and exacerbated the increase in TxB2 production. Glomerular prostaglandin E2 production was not altered by the induction of nephritis nor any of the aforementioned immunologic manipulations. Regression analysis established that glomerular TxB2 production correlated significantly with the leukocyte influx at both 3 and 24 h. Glomerular LTB4 production correlated only with the presence of leukocytes at 3 h. Both glomerular TxB2 and LTB4 production were closely correlated with the renal dysfunction as assessed by proteinuria. These data suggest that leukocytes play a direct critical role in both the functional and metabolic alterations that occur in the setting of NTN. They further imply that leukocytes are crucial to the observed increase in glomerular eicosanoid production.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclooxygenase pathway mediates lung injury induced by phorbol and platelets

The role of platelets in lung injury has not been well defined. In the present study of isolated perfused rat lungs, phorbol myristate acetate (PMA; 0.15 microgram/ml) or platelets (6.7 X 10(4)/ml) alone did not discernibly change the pulmonary arterial pressure (PAP) or lung weight (LW). However, the combination of platelets and PMA drastically increased the PAP and LW (delta PAP 26.2 +/- 1.0 mmHg, delta LW 2.7 +/- 0.4 g). delta PAP was positively correlated with the increase in thromboxane B2 produced by infusion of platelets and PMA (thromboxane B2 = 35.6 + 0.97 delta PAP, r = 0.67, P less than 0.01). The hypertension and edema formation induced by PMA and platelets were strongly attenuated by indomethacin, an inhibitor of platelet cyclooxygenase (delta PAP 5.6 +/- 2.0 mmHg, P less than 0.001; delta LW 0.0 +/- 0.1 g, P less than 0.001), and by imidazole, an inhibitor of thromboxane A2 synthase (PAP 8.0 +/- 2.5 mmHg, P less than 0.001; LW 0.0 +/- 0.3 g, P less than 0.01). Inactivation of platelet lipoxygenase with nordihydroguaiaretic acid mildly depressed pulmonary pressure but did not affect delta LW (delta PAP 18.9 +/- 1.6 mmHg, P less than 0.05; delta LW 3.1 +/- 0.3 g, P greater than 0.05). In vitro experiments showed that the capacity of platelets to release oxygen radicals was only 2.6% of that found for granulocytes. These results suggest that platelets may be activated by PMA to increase PAP and vascular permeability.(ABSTRACT TRUNCATED AT 250 WORDS)