Long-acting PGE2 and Lisinopril Mitigate H-ARS.

Thrombocytopenia is a major complication in hematopoietic-acute radiation syndrome (H-ARS) that increases the risk of mortality from uncontrolled hemorrhage. There is a great demand for new therapies to improve survival and mitigate bleeding in H-ARS. Thrombopoiesis requires interactions between megakaryocytes (MKs) and endothelial cells. 16, 16-dimethyl prostaglandin E2 (dmPGE2), a longer-acting analogue of PGE2, promotes hematopoietic recovery after total-body irradiation (TBI), and various angiotensin-converting enzyme (ACE) inhibitors mitigate endothelial injury after radiation exposure. Here, we tested a combination therapy of dmPGE2 and lisinopril to mitigate thrombocytopenia in murine models of H-ARS following TBI. After 7.75 Gy TBI, dmPGE2 and lisinopril each increased survival relative to vehicle controls. Importantly, combined dmPGE2 and lisinopril therapy enhanced survival greater than either individual agent. Studies performed after 4 Gy TBI revealed reduced numbers of marrow MKs and circulating platelets. In addition, sublethal TBI induced abnormalities both in MK maturation and in in vitro and in vivo platelet function. dmPGE2, alone and in combination with lisinopril, improved recovery of marrow MKs and peripheral platelets. Finally, sublethal TBI transiently reduced the number of marrow Lin-CD45-CD31+Sca-1- sinusoidal endothelial cells, while combined dmPGE2 and lisinopril treatment, but not single-agent treatment, accelerated their recovery. Taken together, these data support the concept that combined dmPGE2 and lisinopril therapy improves thrombocytopenia and survival by promoting recovery of the MK lineage, as well as the MK niche, in the setting of H-ARS.

Mechanism of action of antiplatelet drugs on decompression sickness in rats: a protective effect of anti-GPIIbIIIa therapy.

Literature highlights the involvement of disseminated thrombosis in the pathophysiology of decompression sickness (DCS). We examined the effect of several antithrombotic treatments targeting various pathways on DCS outcome: acetyl salicylate, prasugrel, abciximab, and enoxaparin. Rats were randomly assigned to six groups. Groups 1 and 2 were a control nondiving group (C; n = 10) and a control diving group (CD; n = 30). Animals in Groups 3 to 6 were treated before hyperbaric exposure (HBE) with either prasugrel (n = 10), acetyl salicylate (n = 10), enoxaparin (n = 10), or abciximab (n = 10). Blood samples were taken for platelet factor 4 (PF4), thiobarbituric acid reactive substances (TBARS), and von Willebrand factor analysis. Onset of DCS symptoms and death were recorded during a 60-min observation period after HBE. Although we observed fewer outcomes of DCS in all treated groups compared with the CD, statistical significance was reached in abciximab only (20% vs. 73%, respectively, P = 0.007). We also observed significantly higher levels of plasmatic PF4 in abciximab (8.14 ± 1.40 ng/ml; P = 0.004) and enoxaparin groups (8.01 ± 0.80 ng/ml; P = 0.021) compared with the C group (6.45 ± 1.90 ng/ml) but not CD group (8.14 ± 1.40 ng/ml). Plasmatic levels of TBARS were significantly higher in the CD group than the C group (49.04 ± 11.20 µM vs. 34.44 ± 5.70 µM, P = 0.002). This effect was prevented by all treatments. Our results suggest that abciximab pretreatment, a powerful glycoprotein IIb/IIIa receptor antagonist, has a strong protective effect on decompression risk by significantly improving DCS outcome. Besides its powerful inhibitory action on platelet aggregation, we suggest that abciximab could also act through its effects on vascular function, oxidative stress, and/or inflammation.

Daily prickly pear consumption improves platelet function.

Prickly pear is traditionally used by Pima Indians as a dietary nutrient against diabetes mellitus. We examined the effect of daily consumption of 250 g in 8 healthy volunteers and 8 patients with mild familial heterozygous hypercholesterolemia on various parameters of platelet function. Beside its action on lipids and lipoproteins, prickly pear consumption significantly reduced the platelet proteins (platelet factor 4 and beta-thromboglobulin), ADP-induced platelet aggregation and improved platelet sensitivity (against PGI2 and PGE1) in volunteers as well as in patients. Also plasma 11-DH-TXB2 and the WU-test showed a significant improvement in both patients and volunteers. In contrast, collagen-induced platelet aggregation and the number of circulating endothelial cells showed a significant response in patients only. No influence of prickly pear ingestion on peripheral platelet count was monitored. The dietary run-in period did not influence any of the parameters of haemostasis examined. No sex difference was seen. Prickly pear may induce at least part of its beneficial actions on the cardiovascular system via decreasing platelet activity and thereby improving haemostatic balance.

Lack of effect of fish oil supplementation on coagulation and transcapillary escape rate of albumin in insulin-dependent diabetic patients with diabetic nephropathy.

OBJECTIVE: We studied the effect of a diet supplementation with fish oil in insulin-dependent diabetic patients with nephropathy in order to evaluate whether abnormal transcapillary escape rate of albumin and procoagulant activity in these patients could be modified. METHODS: A double-blind, randomized, controlled study was carried out at a tertiary referral centre. The subjects were 29 insulin-dependent diabetic patients with nephropathy. One year of fish oil supplementation (4.6 g n-3 fatty acids/day) was compared with placebo (olive oil). The main outcome measures were N-3 fatty acid proportions of platelet lipids, transcapillary escape rate of albumin, prothrombin fragment 1 + 2, thrombin-antithrombin complexes, markers of fibrinolysis, fibrinogen, factor VII antigen and activity, thrombomodulin, von Willebrand factor, platelet factor 4 and beta-thromboglobulin. These were measured every 6 months. RESULTS: Neither transcapillary escape rate of albumin (7.4 (median) (5.0-9.8) (range) % vs. 7.0 (4.6-10.6) %) nor prothrombin fragment 1 + 2 (0.97 (0.72-2.40) nmol/L vs. 1.01 (0.59-3.11) nmol/L) changed after 12 months of fish oil supplementation. CONCLUSION: Increased transcapillary escape rate of albumin and activity could not be modified during diet supplementation with fish oil in insulin-dependent diabetic patients with nephropathy.

Novel tocotrienols of rice bran suppress cholesterogenesis in hereditary hypercholesterolemic swine.

A tocotrienol-rich fraction (TRF(25)) and novel tocotrienols (d-P(21)-T3 and d-P(25)-T3) of rice bran significantly lowered serum and low density lipoprotein cholesterol levels in chickens. The present study evaluated the effects of novel tocotrienols on lipid metabolism in swine expressing hereditary hypercholesterolemia. Fifteen 4-mo-old genetically hypercholesterolemic swine were divided into five groups (n = 3). Four groups were fed a corn-soybean control diet, supplemented with 50 microg of either TRF(25), gamma-tocotrienol, d-P(21)-T3 or d-P(25)-T3 per g for 6 wk. Group 5 was fed the control diet for 6 wk and served as a control. After 6 wk, serum total cholesterol was reduced 32-38%, low density lipoprotein cholesterol was reduced 35-43%, apolipoprotein B was reduced 20-28%, platelet factor 4 was reduced 12-24%, thromboxane B(2) was reduced 11-18%, glucose was reduced 22-25% (P<0.01), triglycerides were reduced 15-19% and glucagon was reduced 11-17% (P<0.05) in the treatment groups relative to the control. Insulin was 100% greater (P<0.01) in the treatment groups than in the control group. Preliminary data (n = 1) indicated that hepatic activity of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase was lower in the treatment groups, and cholesterol 7alpha-hydroxylase activity was unaffected. Cholesterol and fatty acid levels in various tissues were lower in the treatment groups than in control. After being fed the tocotrienol-supplemented diets, two swine in each group were transferred to the control diet for 10 wk. The lower concentrations of serum lipids in these four treatment groups persisted for 10 wk. This persistent effect may have resulted from the high tocotrienol levels in blood of the treatment groups, suggesting that the conversion of tocotrienols to tocopherols may not be as rapid as was reported in chickens and humans.

Effects of nisoldipine on cytosolic calcium, platelet aggregation, and coagulation/fibrinolysis in patients with coronary artery disease.

The effect of nisoldipine, a dihydropyridine Ca2+ antagonist, on the platelet cytosolic Ca2+ concentration ([Ca2+]i), platelet aggregation, and various coagulation and fibrinolysis parameters was assessed in normotensive patients with coronary artery disease (CAD). Eleven patients with angiographically confirmed CAD (4 men, 7 women aged 67.3 +/- 5.4 years) were administered nisoldipine at 10 mg/day for two weeks. The [Ca2+]i was determined by use of fura2-loaded platelets, platelet aggregation was measured with an aggregometer, and coagulation/fibrinolysis parameters were measured by standard methods. Nisoldipine did not significantly affect blood pressure or heart rate. However, the [Ca2+]i decreased significantly (P<0.05) and platelet aggregation was also significantly inhibited. Plasma D-dimer levels decreased significantly (P<0.01). Thus, nisoldipine not only suppressed platelet activation but also affected the coagulation system, suggesting that it is not only a vasodilator and platelet inhibitor but also an antithrombotic agent.

Calcium supplementation attenuates an enhanced platelet function in salt-loaded mildly hypertensive patients.

We designed this study to evaluate the effect of low versus high calcium intake on platelet function in salt-loaded patients with mild hypertension. After a 7-day period of dietary salt restriction, 19 patients were placed on a high salt (300 mmol/d), low calcium (6.25 mmol/d) diet for 7 days; 10 of these patients were given 54 mmol/d of supplementary calcium, and 9 patients were given placebo. At the end of the low and high salt regimens, we evaluated changes in blood pressure, platelet aggregation, and the platelet release reaction measured as plasma beta-thromboglobulin and platelet factor 4 levels. With high salt intake, significant increases in mean blood pressure (P < .02), red blood cell sodium (P < .01), and platelet aggregation induced by 3 mumol/L ADP (P < .01) and by 3.0 mg/L epinephrine (P < .05) were observed in the placebo-treated patients but not in the calcium-supplemented ones. Compared with the placebo-treated patients, calcium-supplemented patients had a smaller weight gain (P < .05) but excreted more sodium and calcium (P < .01) at the end of the high salt regimen. Calcium supplementation resulted in decreases in beta-thromboglobulin (P < .05), platelet factor 4 (P < .01), and plasma and urinary excretions of norepinephrine (P < .02) during the high salt, low calcium regimen. The decrease in plasma norepinephrine correlated positively with the decreases in beta-thromboglobulin (r = .72, P < .02) and platelet factor 4 (r = .85, P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet activation in the lung after antigen challenge in a model of allergic asthma.

The purpose of this study was to investigate whether platelets are activated and release their products in the human lung after antigen challenge. Using subsegmental antigen challenge as a model of asthma, bronchoalveolar lavage fluids from ragweed-allergic asthmatic subjects were assayed for the alpha granule products, platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG), prior to challenge (baseline) and at 5 min and 19 h after challenge with ragweed antigen. Airway segments challenged with normal saline were used as controls. Five minutes after antigen challenge, levels of platelet products in BAL fluid were not elevated from baseline or normal saline control levels. However, 19 h after antigen challenge, a 10-fold increase in platelet products in BAL fluids was found. The mean PF4 levels increased from baseline and saline control values of less than 1.0 to 7.2 ng/ml (p less than 0.05) 19 h after antigen challenge. beta-TG increased from baseline and control levels of less than 1.0 to 6.6 ng/ml (p less than 0.05). Elevations in PF4 and beta-TG were highly correlated with each other (r = 0.98, p less than 0.0001). Levels of platelet products during the 19-h response correlated with albumin, with kinins, with the prostaglandins 6-keto-PGF1 alpha, PGE2, and PGF2 alpha, and with the eosinophil-derived proteins, eosinophil-derived neurotoxin and eosinophil peroxidase. We conclude that platelet activation in the lung is a feature of the late inflammatory response to antigen challenge and that platelets may play an important role in allergic inflammation and asthma.

[Effects of Ligusticum wallichii on the plasma levels of beta-thromboglobulin, platelet factor 4, thromboxane B2 and 6-keto-PGF1 alpha in patients with acute cerebral infarction].

By using ELISA and RIA to measure the levels of Beta-thromboglobulin (beta-TG), platelet factor 4(PF4), thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) in plasma of patients with acute cerebral infarction, the authors found that the levels of beta-TG, PF4 and TXB2 in plasma had significantly increased (P less than 0.01), but the level of 6-keto-PGF1 alpha in plasma showed no change (P greater than 0.05). The results of the Ligusticum wallichii (Ligusticum) treatment to the test-group showed that the levels of beta-TG, PF4 and TXB2 in plasma had significantly decreased (P less than 0.01), and the level of 6-keto-PGF1 alpha in plasma had significantly increased (P less than 0.05). This suggested that the Ligusticum treatment could effectively inhibit the platelet activation in vivo and correct the TXA2-PGI2 imbalance in blood of the patients. In this study, some new approaches were explored to explain the mechanisms of Ligusticum for preventing and treating cerebral ischemia.

[Relation of coronary heart disease based on traditional Chinese medicine syndrome differentiation and prostaglandin, blood platelet function, and protein C].

The relationship between 68 cases of thromboxane B2(TXB2), 6-keto-prostaglandin F1 alpha (6-K-PGF1 alpha), beta-thromboglobulin (beta TG), platelet factor 4 (PF4), protein C antigen (PC:Ag), total-proteins (T-Ps) with coronary heart disease (CHD) based on TCM syndrome differentiation were studied. 45 cases of male, 23 cases of female, they were divided into 30 cases of blood stasis group and 38 cases of Qi syndrome group. 39 healthy subjects of same age and sex were chosen as the control group. The results were as follows: The TXB2, beta TG, PF4 in CHD were higher than those of control. 6-K-PGF1 alpha was lower (P less than 0.05, P less than 0.01) respectively. The TXB2 in blood stasis was significantly higher than that of Qi syndrome while the 6-K-PGF1 alpha in Qi Syndrome was significantly lower than that of blood stasis syndrome (P less than 0.01). The PC:Ag, T-Ps in CHD were higher than those of the control. The PC:Ag in blood stasis was lower and was higher in Qi syndrome (P less than 0.01). It showed that microthrombosis formed in blood stasis group caused blood flow slowly, while coronary-pathy and/or coronary spasm were the major pathologic change in Qi syndrome. Elevated PC:Ag, T-Ps in Qi syndrome showed that there were complementary action to hypercoagulation in Qi syndrome to eliminate coagulation factor to prevent coagulation happening and stimulation of fibrinolysin activator, promoting fibrinogenolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary tocotrienols reduce concentrations of plasma cholesterol, apolipoprotein B, thromboxane B2, and platelet factor 4 in pigs with inherited hyperlipidemias.

Normolipemic and genetically hypercholesterolemic pigs of defined lipoprotein genotype were fed a standard diet supplemented with 50 micrograms/g tocotrienol-rich fraction (TRF) isolated from palm oil. Hypercholesterolemic pigs fed the TRF supplement showed a 44% decrease in total serum cholesterol, a 60% decrease in low-density-lipoprotein (LDL)-cholesterol, and significant decreases in levels of apolipoprotein B (26%), thromboxane-B2 (41%), and platelet factor 4 (PF4; 29%). The declines in thromboxane B2 and PF4 suggest that TRF has a marked protective effect on the endothelium and platelet aggregation. The effect of the lipid-lowering diet persisted only in the hypercholesterolemic swine after 8 wk feeding of the control diet. These results support observations from previous studies on lowering plasma cholesterol in animals by tocotrienols, which are naturally occurring compounds in grain and palm oils and may have some effect on lowering plasma cholesterol in humans.

Eicosapentanoic acid suppresses intimal hyperplasia after expanded polytetrafluoroethylene grafting in rabbits fed a high cholesterol diet.

The effect of purified eicosapentanoic acid on intimal fibrous hyperplasia in expanded polytetrafluoroethylene grafts was examined in 18 rabbits undergoing infrarenal aorta reconstruction. Six rabbits received commercial rabbit chow (control group), six a regular diet supplemented with 1% cholesterol (cholesterol group), and six the cholesterol diet with 91.1% pure eicosapentanoic acid 500 mg/day (eicosapentanoic acid group). Grafts were harvested 3 months after surgery for histologic examination. The platelet count and serum beta-thromboglobulin and platelet factor 4 concentrations were not significantly different between groups. Serum arachidonic acid level in the cholesterol group was significantly higher than in the control group, and serum eicosapentanoic acid levels in the eicosapentanoic acid group were significantly higher than in the remaining two groups. Intergroup differences in serum 6-keto-prostaglandin F1 alpha and thromboxane B2 concentrations were not significant. Intimal thickness at midgraft was 5.2 +/- 6.2 microns in the control group, 67.6 +/- 46.9 microns in the cholesterol group, and 19.2 +/- 18.4 microns in the eicosapntanoic acid group. intimal thickness in the cholesterol group was greater than in either the control or licosapentanoic acid group (p less than 0.01 and p less than 0.05, respectively). These data suggest that eicosapentanoic acid reduces intimal fibrous proliferation in expanded polytetrafluoroethylene grafting as a result of hypercholesterolemia and that this effect is independent of the platelet count, activated platelet factors, and the prostacyclin/thromboxane A2 ratio.

[Effects of Ligusticum wallichii on the plasma levels of beta-thromboglobulin, platelet factor 4, thromboxane B2 and 6-keto-PGF1 alpha in rabbits under acute experimental cerebral ischemia].

By occluding the bilateral carotid arteries of rabbits to produce bilateral partial cerebral ischemia, and by using RIA and ELISA to measure the levels of Beta-thromboglobulin (beta-TG), platelet factor 4 (PF4), thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) in plasma, the authors found that the levels of beta-TG, PF4 and TXB2 in plasma had significantly increased (P less than 0.01), but the level of 6-keto-PGF1 alpha in plasma showed no change (P greater than 0.05) after cerebral ischemia appeared. The results of the Ligusticum wallichii (Ligusticum) pre-treatment to the test-group showed that the levels of beta-TG, PF4 and TXB2 in plasma had significantly decreased (P less than 0.01), and the level of 6-keto-PGF1 alpha in plasma had significantly increased (P less than 0.05). This suggested that the Ligusticum treatment could effectively inhibit the platelet activation in vivo and correct the TXA2-PGI2 imbalance in blood after cerebral ischemia. In this study, some new approaches were explored to explain the mechanisms of Ligusticum for preventing and treating cerebral ischemia.

Effects of a PAF-antagonist (BN 52063) on bronchoconstriction and platelet activation during exercise induced asthma.

1. The effects of a specific PAF acether antagonist (BN 52063) on the response to isocapnic hyperventilation with dry cold air (ISH study) and exercise (EIA study) were assessed in a single dose and short term treatment study in 10 patients with exercise induced asthma. 2. ISH challenge was performed twice within 1 h after administration of either placebo, 240 mg BN 52063 p.o. or inhalation of 2.4 mg BN 52063. Hyperventilation increased Raw from 0.30 +/- 0.02 to 0.89 kPa s l-1 (P less than 0.001) after the first challenge and from 0.28 +/- 0.04 to 0.84 +/- 0.06 kPa s l-1 (P less than 0.001) after the second challenge. Oral pretreatment with BN 52063 did not result in a reduction of bronchoconstriction during both challenges. A significant increase of Raw was noted immediately after inhalation of BN 52063. An inhibition of PAF induced platelet aggregation (by a factor of 2) occurred after oral administration of BN 52063 after both ISH challenges (P less than 0.05). No significant inhibition of PAF induced platelet aggregation was seen after inhalation of BN 52063. At concentrations up to 30 microM in vitro, BN 52063 inhibited PAF induced platelet aggregation in a dose dependent manner. The IC50 of BN 52063 against the aggregating effect of 1 microM PAF was 7.0 +/- 2.1 microM. 3. In the EIA study the patients were challenged on the third day of treatment with either placebo or 240 mg BN 52063 p.o. or 5 mg BN 52063 by inhalation. Peak expiratory flow rates (PEFR) fell by 155 +/- 37 1 min-1 after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

[Platelet factor 4 levels in full-term newborns undergoing phototherapy]. / Livelli di fattore piastrinico 4 (FP4) in neonati a termine sottoposti a fototerapia.

PF4 levels and platelets counts were studied in a group of 15 term newborn infants before treatment and after 24-48-72 and 96 hours of phototherapy and in a control group of 10 babies. Unlike data found by other AA. in vitro and in preterm infants, our values show only minimal, not statistically significant, differences in PF4 levels and platelets counts between the two groups. The AA. believe that in term infants, with adequate weight for gestational age, proper phototherapy treatment does not cause any change in platelet function, owing to the thicker and more mature skin and to the better bone marrow compensation typical of term versus preterm infants.

Plasma platelet factor 4 response in rhesus monkeys fed coconut oil.

Platelet factor 4 (PF 4), the low molecular weight polypeptide stored in the alpha granule, has been shown to be released from platelets during the process of activation. To examine the effects of known atherogenic food fats on platelet activation, as manifested in circulating PF 4 concentrations, groups of rhesus monkeys were fed diets enriched with varying quantities of different food fats. Plasma PF 4 levels were measured at set intervals during the experimental period. Platelet counts were performed and PF 4 values assayed using the radioligand binding technique. Animals given coconut-oil-enriched diets showed the greatest increase in PF 4 levels; while those fed corn, peanut and soybean-oil-containing rations showed small insignificant fluctuations of plasma PF 4 values. In this study the coconut oil effect on plasma PF 4 values increased with time; diluting the coconut oil with increasing quantities of corn oil led to progressive decreases in these values. These data indicate an increased incidence of platelet activation in animals fed coconut-oil-enriched diets, and suggest that corn oil counteracts this thromboactive effect of coconut oil.

In vivo indexes of platelet and vascular function during fish-oil administration in patients with atherosclerosis.

Populations that consume a diet rich in marine lipids may have a lower risk of atherosclerotic disease. Fish oil contains the N-3 polyunsaturated fatty acid eicosapentaenoate, and the biosynthesis of thromboxanes and prostacyclins from eicosapentaenoate (thromboxane A3 and prostaglandin I3), rather than from the usual precursor arachidonate (thromboxane A2 and prostaglandin I2), may help to reduce the risk. To examine this hypothesis, we studied the effect of eicosapentaenoate supplementation (10 g per day) for one month on the synthesis of thromboxanes and prostacyclins, as assessed by urinary metabolite excretion, in six patients with peripheral vascular disease and seven normal controls. Supplementation markedly increased the eicosapentaenoate content of phospholipids from red cells and platelets. Synthesis of the platelet agonist thromboxane A2, which was elevated in the patients at base line, declined by 58 percent during supplementation but did not reach normal values. The decline in thromboxane A2, which is synthesized from arachidonate, coincided with the formation of the inactive thromboxane A3, which is synthesized from eicosapentaenoate. A lower dose of eicosapentaenoate (1 g per day) was not sufficient to maintain the changes in thromboxane A2 synthesis. Platelet function was only moderately inhibited during eicosapentaenoate supplementation, consistent with incomplete suppression of thromboxane A2 synthesis. These studies show that a high dose of eicosapentaenoate alters the pattern of synthesis of thromboxanes and prostacyclins. However, effects comparable to those of aspirin require long-term administration in high doses. Whether other properties of fish oil might render it a more attractive antithrombotic therapy remains to be determined.