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.

8-Epi-PGF2alpha and 6-oxo-PGF1alpha in human (varicose) veins: influence of age, sex, and risk factors.

The isoprostane 8-epi PGF2alpha is a vasoconstrictive, mitogenic, proliferative, and mild proaggregatory agent. We examined 8-epi-PGF2alpha and 6-oxo-PGF1alpha from venous tissue derived from varicose (venous) surgery by means of a specific radioimmunoassay. A total of 336 samples from 82 patients (50 females, 32 males; aged 22-68 years) were examined. Tissue samples were classified according to normal, dilated, and varicose. Of these, 94 samples from 31 patients (20 females, 11 males; aged 29-64 years) with additional risk factors (cigarette smoking, hyperlipidemia, diabetes mellitus) were determined in the same way. Mean absolute values for 6-oxo-PGF1alpha are not significantly higher for dilated segments followed by varicose and intact samples. No significant age and sex differences can be monitored. Presence of risk factors, however, results in a significantly diminished 6-oxo-PGF1alpha, irrespective of morphology. 8-Epi-PGF2alpha again showed no age and sex dependence, its presence in varicose segments, however, was significantly (p<0.01) decreased. Risk factors resulted in a significantly increased 8-epi-PGF2alpha. These data indicate that the influence of risk factors on vasomodulatory (iso-)eicosanoids of human veins is more pronounced than the actual morphologic stage. Lower 8-epi-PGF2alpha in varicose veins may shift the venous tone toward vasodilatation and contribute to development and progression of varicosis.

Effect of giving up cigarette smoking and restarting in patients with clinically manifested atherosclerosis.

Cigarette smoking, a key risk factor for the development of vascular disease, is associated with an increased 8-epi-prostaglandin (PG) F(2alpha). Elevated 8-epi-PGF(2alpha) has been found in vascular tissue, blood and urine as well. We examined the influence of quitting cigarette smoking in 71 patients (38 males, 33 females; aged 32-67 a) with clinically manifested atherosclerosis and various risk factors. In addition, in eight patients with hypercholesterolemia without clinical manifestation of atherosclerosis quitting smoking was monitored as well. Twenty-six of the patients with manifested atherosclerosis and five with hypercholesterolemia restarted and the isoprostanes in plasma, serum and urine were monitored in these patients as well. Quitting cigarette smoking induces an immediate decline becoming significant after 1 or 2 weeks. Restarting smoking results in an increase in 8-epi-PGF(2alpha) reaching prevalues within almost 1 week. These findings indicate that the in vivo oxidation injury associated with cigarette smoking quickly decreases after quitting but increases soon after restarting immediately.

Effect of black tea on (iso-)prostaglandins and platelet aggregation in healthy volunteers.

Flavonoids among others are found in tea. Many of them were shown to exhibit antioxidative action in vitro. We examined the effect of a 1-month consumption of 500 ml black tea containing 2.0 mg quercetin. While single tea consumption 2 h after finishing the intake did not affect any of the parameters (8-epi-PGF(2 alpha) in plasma and serum, 11-DH-TXB(2) and ADP-induced platelet aggregation) examined at all, 1-week consumption and even more than 1 month regular tea intake significantly decreased most of the parameters. The effect was somewhat more pronounced for females as compared with males, the values for 11-dehydro-thromboxane B(2) (11-DH-TXB(2)) and ADP-induced aggregation reached the level of significance in females only. These data show that regular daily black tea consumption for 1 month improves platelet function and decreases thromboxane and 8-epi-PGF(2 alpha) to a varying extent indicating a reduced in vivo oxidation injury.

Regular ingestion of opuntia robusta lowers oxidation injury.

The influence of opuntia robusta (prickly pear), a traditionally used dietary nutrient against diabetes mellitus among the American Indian population, was examined in 15 young patients suffering from familial heterozygous isolated hypercholesterolemia. Oxidation injury was determined via 8-epi-PGF(2 alpha)in plasma, serum and urine. Daily consumption of 250 g broiled edible pulp of prickly pear had no influence on body weight and body fat composition. Total cholesterol was lowered (P<0.01) as was LDL-cholesterol (P<0.04). No significant changes were observed either in triglycerides or in HDL. Prickly pear induced a significant decrease in plasma (27.9+/-3.3-->25.6+/-3.2;P<0.03), serum (302.0+/-11.4-->283.2+/-14.5;P<0.0003) and urinary (355.9+/-18.4-->323.9+/-16;P<0.00002) 8-epi-PGF(2alpha)values. The findings on a decrease of 8-epi-PGF(2alpha)were more pronounced in females than in males, the highest significance being found in urine, while, in contrast, the effects on total- and LDL-cholesterol were more pronounced in males. A prerunning 4 weeks period of dietary counseling had no significant effect on either of the parameters examined. These findings indicate that the regular ingestion of opuntia robusta is able to significantly reduce in-vivo oxidation injury in a group of patients suffering from familial hypercholesterolemia. This traditional food of the American Indians thus may have a significant cardiovascular benefit.

Increase of isoprostane 8-epi-PGF(2alpha)after restarting smoking.

Isoprostanes are known as reliable markers of in vivo oxidation injury. Cigarette smoking has been shown to be associated with a significant increase in 8-epi-PGF(2alpha), a major member of this family of compounds. Quitting smoking reduces 8-epi-PGF(2alpha) values to normal within a couple of weeks only. In this follow-up we checked the 8-epi-PGF(2alpha), values in plasma, serum and urine in 28 people who restarted smoking after a quitting attempt of various duration. 8-epi-PGF(2alpha)shows a certain increase after restarting smoking reaching a maximum after already 1 week. Continuation of smoking does not significantly further increase 8-epi-PGF(2alpha). These data indicate a fast response of restarting as on quitting smoking on in vivo oxidation injury. The oxidation injury reflected by 8-epi-PGF(2alpha)may be a key pathogenetic mechanism in smoking-induced vascular injury.

6-oxo-PGF(1 alpha)and 8-epi-PGF(2 alpha)in the arterial wall layers of various species: a comparison between intact and atherosclerotic areas.

PGI(2)and 8-epi-prostaglandin(PG)F(2 alpha)are antagonizing compounds. For both a key role in vascular pathology has been hypothesized. The isoprostane 8-epi-PGF(2 alpha)and the stable derivative of PGI(2), 6-oxo-PGF(1 alpha)were determined immunologically in the arterial wall of various species including humans. Human arterial tissue contained the highest amounts of 8-epi-PGF(2 alpha)and synthesized the lowest PGI(2). A significant negative correlation between 8-epi-PGF(2 alpha)and 6-oxo-PGF(1 alpha)was observed. Atherosclerotic segments showed significantly higher 8-epi-PGF(2 alpha)and lower 6-oxo-PGF(1 alpha). 8-epi-PGF(2 alpha)in the intima was higher than in the media, the highest amounts being found in foam-cell rich areas. Synthetic (activated) smooth muscle cells were associated with an enhanced 8-epi-PGF(2 alpha)as well as 6-oxo-PGF(1 alpha). Tissue samples derived from smokers contained more 8-epi-PGF(2 alpha)and produced less PGI(2). The by far highest 8-epi-PGF(2 alpha)/6-oxo-PGF(1 alpha)ratio was found in foam cell rich areas. Similar findings were obtained in rabbit and in minipig arteries. The total 8-epi-PGF(2 alpha)/6-oxo-PGF(1 alpha)ratio is low in normal tissue, increases significantly in an active atherosclerotic process and seems to be even further increased in an inactive atherosclerotic process. These findings are providing an information on the extent of oxidation injury at various sites of different types of atherosclerotic process.

Quitting cigarette smoking results in a fast improvement of in vivo oxidation injury (determined via plasma, serum and urinary isoprostane).

Isoprostanes (IP) have been identified as reliable markers of in vivo oxidation injury. Recently, in vascular tissue and blood as well as urine of cigarette smokers, increased IP values have been discovered. We examined 47 adults (26 males, 21 females; aged 30-66 years), admitted to a cardiovascular unit on an outpatient basis, with various risk factors but without any sign of manifestation of atherosclerosis. Refraining from cigarette smoking for a few days resulted in a significant drop of plasma, serum, and urinary 8-epi-PGF(2alpha). Thereafter, a further continuous decrease was monitored, reaching a steady state after about 4 weeks after quitting cigarette smoking. Prevalues of 8-epi-PGF(2alpha) were higher, depending on the type and number of risk factors; the decrease after quitting, however, was comparable. These results indicate that exsmokers may rapidly recover from their enhanced in vivo oxidation.

Isoprostanes quickly normalize after quitting cigarette smoking in healthy adults.

BACKGROUND: Isoprostanes and in particular 8-epi-PGF2 alpha have been claimed as a useful measure for invivo oxidation injury. While smokers show elevated 8-epi-PGF2 alpha the behaviour during quitting smoking is unknown. METHODS AND RESULTS: We determined 8-epi-PGF2 alpha in 7 healthy adults ready to quit smoking in plasma, serum and urine by means of an enzyme immunoassay after extraction and purification before quitting smoking and during a follow-up period of 4 weeks. After quitting smoking, 8-epi-PGF2 alpha shows a rapid decline within a few days almost completely normalizing within 4 weeks. CONCLUSION: The cigarette-smoking associated invivo oxidation injury almost completely disappears within 4 weeks of quitting smoking.

Prostaglandin synthesis in human lymphatics from precursor fatty acids.

(Iso)-eicosanoids appear to play a pivotal role in lymphatic contractility. Because prostaglandin (PG)I2, an arachidonic acid (20:4) metabolite, is a key substance generated by human lymphatics, both from exogenous and endogenous substrates, it is reasonable to assume that altered nutritional intake of precursor fatty acids (FA) influences formation of respective eicosanoids qualitatively and quantitatively, and thereby modify its biological effects on human lymphatics. We, therefore, examined the effect of 2 other FA-precursors, dihomo-gamma-linolenic (20:3) and eicosapentaenoic acid (20:5) on the formation of the respective PG-metabolites in human lymphatics removed from the legs in patients undergoing amputation after traumatic injury. 20:3 and 20:5 were poorer substrates to form PGs. Because these PGs exert different biological actions and their synthesis may be altered by vascular environmental risk factors such as cigarette smoking, diabetes mellitus, hyperlipidemia, and availability of FA precursors and therefore nutrition, PGs may profoundly modulate the lymphatic contractile response under a variety of circumstances. The full effect of all the formed compounds of the 1- and 3-series PGs on lymph vessel contractility, however, still needs to be tested.

LDL-apheresis decreases plasma levels and urinary excretion of 8-epi-PGF2alpha.

Isoprostanes (IP) generated during free radical catalyzed oxidation injury have been claimed as a reliable indicator of oxidative stress in vivo. In particular, they are formed during LDL-oxidation. Vascular content, plasma levels and urinary excretion of IP were reported to be elevated in hypercholesterolemia. We therefore assessed the values of the IP 8-epi-PGF2alpha in plasma and urine in nine patients (7 males, 2 females) suffering from severe heterozygous hypercholesterolemia before and after LDL-apheresis as well as during the interval. LDL-apheresis caused a significant (P<0.01) drop in 8-epi-PGF2alpha in plasma and urine. The respective values in smokers (n = 4) were significantly (P<0.01) higher as compared to non-smokers. No sex difference was seen. Together with the findings of a parallel decrease in oxidized LDL, these data show a significant benefit of LDL-apheresis reducing in vivo oxidation injury. This benefit may at least partly contribute to the clinical improvement seen in the patients treated.

Eicosanoid production and lymphatic responsiveness in human cigarette smokers compared with non-smokers.

Leg lymphatic segments were isolated from 10 patients (4 cigarette smokers and 6 non-smokers) undergoing conventional lymphography. Prostaglandin (PG) levels and PG synthesis in the lymphatics and in a variety of body fluids and the effects of eicosanoids on lymphatic contractility were determined. Leg lymphatics from 4 smokers generated less PGI2 and contained more 8-epi-PGF2 alpha when compared with leg lymphatics in 6 non-smokers. Similarly, levels of 8-epi-PGF2 alpha in smokers compared with non-smokers were higher in plasma (28.6 cf 19.7 pg/ml), leg lymph (146.7 cf 65.3 pg/ml), serum (299.0 cf 204.1 pg/ml), and urine (473.4 cf 241.0 pg/mg creatinine). Lymphatics from smokers also showed a higher contractile response, less 14C-arachidonic acid conversion to PGI2 and less PGI2-formation with various stimuli compared with non-smokers. Together these findings suggest that smoking induces oxidation injury, promotes altered (iso-)eicosanoid production and impacts on the function and dysfunction of peripheral lymphatics under normal circumstances and in a variety of clinical disorders.

Isoprostanes in atherosclerosis.

Isoprostanes (IP) are a new family of compounds formed during oxidation injury. 8-epi-prostaglandin (PG) F2alpha, a vasoconstrictory and mitogenic substance, is increased in hyperlipidemia in blood and urine as well as at the vascular level in the intima, in particular along foam cells. Similarly, cigarette smoking is associated with an immediate increase in 8-epi-PGF2alpha and a quick drop after quitting. Also diabetes and even the more a combination of risk factors (for the development of atherosclerosis) results in increased 8-epi-PGF2alpha in various compartments. Others, such as sex, age, hypertension and obesity were of minor influence. These findings further indicate, that in-vivo oxidation injury as reflected by increased IP may play a relevant role in atherogenesis. IP may serve as useful markers to assess oxidation injury at a local level.

Maternal cigarette smoking increases F2-isoprostanes and reduces prostacyclin and nitric oxide in umbilical vessels.

The objective of this study was to evaluate the influence of smoking on F2-isoprostanes, prostacylin and nitric oxide in human umbilical vessels. Umbilical cords from 13 babies of smoking mothers and from 28 babies of non-smoking mothers were examined for levels of F2-isoprostanes, prostacyclin, L-arginine, and L-citrulline. Forty-one umbilical arteries and eleven umbilical veins were analyzed. Statistical analysis of data was done using modified t-test. Cigarette smoking increased F2-isoprostane levels and reduced the generation of prostacyclin, L-arginine and L-citrulline comparably in umbilical arteries and veins. Notably, in umbilical cords of babies of non-smoking mothers the F2-isoprostane level was significantly higher in arteries. Cigarette smoking correlates with a direct vasoconstrictive effect. We suggest that smoking might enhance the vasoconstrictory capacity in umbilical arteries by increased F2-isoprostanes and by a simultaneous decrease in the production of the vasodilatory compounds, prostacyclin, and nitric oxide.

Increased plasma, serum and urinary 8-epi-prostaglandin F2 alpha in heterozygous hypercholesterolemia.

Oxidation injury results in foam cell formation, which is known to be a central mechanism in atherogenesis. We investigated in this study whether 8-epi-prostaglandin (PG) F2 alpha, an in vivo indicator of oxidative stress, is elevated in hyperlipoproteinemia. The isoprostane 8-epi-PGF2 alpha levels in plasma, serum and urine were determined in 123 patients (67 m, 56 f; 17-60 years) suffering from familial heterozygous hypercholesterolemia (FH). A group of 99 normocholesterolemic adults (51 m, 48 f; 20-63 years) served as controls. Plasma, serum and urine levels of 8-epi-PGF2 alpha were significantly (p < 0.01) higher in the FH group. Smokers showed elevated 8-epi-PGF2 alpha levels; however, no correlation was observed to hypertension, age and sex. Successful dietary and drug treatment of FH patients resulted in a significant decrease in 8-epi-PGF2 alpha levels in plasma, serum and urine. These findings indicate that FH is associated with increased oxidation injury, which is beneficially influenced by successful dietary and/or drug treatment.

Isoprostane 8-epi-prostaglandin F2 alpha is a potent contractor of human peripheral lymphatics.

Isoprostanes are products of free radical-catalyzed peroxidation and 8-epi-prostaglandin (PG) F2 alpha is the most important vasomodulator of this group of compounds. In human lower leg lymphatics isolated from 5 different patients without a smoking history or hyperlipidemia, 8-epi-PGF2 alpha stimulated in vitro contraction more strongly than the thromboxane receptor agonist U46619. Other isoprostanes (8-epi-PGE1, 8-epi-PGE2) had only limited lymphatic contractile potency. These data suggest a potentially relevant role for epi-8-PGF2 alpha in facilitating lymph transport especially in conditions of inflammation.

[Isoprostanes, a new substance group in angiology--of future significance?]. / Isoprostane, eine neue Substanzgruppe in der Angiologie--in der Zukunft von Bedeutung?

F2-isoprostanes are prostaglandin F2-like compounds being formed by non-enzymatic peroxidation of arachidonic acid in vivo. They have a variety of biological actions. The most important compound of this group is 8-epi-PGF(2 alpha) being capable to induce vasconstriction in particular of lung- and renal vascular tissue. Isoprostanes are present in esterified form; in free form they become available after hydrolysis by phospholipase A. An increase in isoprostanes is an important indicator of oxidative stress in-vivo due to a variety of different noxi such as metal- or non-metal ions for cigarette smoke. Isoprostanes show an activation of platelets; as a consequence of the interaction of 8-epi-PGF(2 alpha) with specific receptors platelet aggregation may be induced or may be enhanced together with other agonists. Due to these preliminary results isoprostanes could become an interesting substance in angiology in the future for diagnosis of oxidative stress as well as in the understanding of the pathogenesis of atherosclerosis.

[Single passive smoking exposure induces no measurable oxidation of low density lipoproteins]. / Einmaliges Passivrauchen induziert keine messbare Oxidation der low-density Lipoproteine.

Oxidation of low-density lipoproteins (LDL) is well known to increase the atherogenic risk. Active smoking has been claimed to be associated with a significant oxidant stress determined by enhanced LDL oxidation and isoprostane formation. We assessed the susceptibility of LDL to oxidation in 9 healthy non-smokers and 7 smokers before and after three and five hours' exposure to passive smoking. Baseline values for the lag time, diene formation, malondialdehyde and isoprostanes differed in part significantly. In contrast to the data on active smoking, passive exposure to cigarette smoke did not significantly affect any of these parameters, nor diene formation and electrophoretic mobility in smokers and non-smokers alike. These results indicate that a single exposure to passive smoking does not induce relevant oxidation of LDL in men.

The effect of NO/EDRF and monocytes/macrophages on LDL-oxidation.

Beside prostaglandin (PG) I2 and tissue plasminogen activator (tPA), nitric oxide (NO) is a key fepellant substance contributing to haemostatic balancing. The role of low-density lipoproteins (LDL) in the pathogenesis of atherosclerosis has been gaining increasing importance. It is well accepted that LDL in their modified (i.e. oxidized) form are no longer recognized by the LDL-receptor, but are taken up by cells of the arterial wall, especially macrophages, in a non-regulated manner through the so called scavenger-receptor pathway. This process leads to the formation of foam cells, the hallmark of the atherosclerotic lesion. NO is also produced in relevant amounts by macrophages. The interaction of NO and LDL with macrophages is thus of key importance in the onset of early lesions. While oxidized LDL (oxLDL) are resulting in a decreased NO availability, NO seems to prevent LDL-oxidation. In contrast, however, in the presence of superoxides oxidation may result. All these potential actions have to be discussed in view of the extremely short half-life of NO indicating that these actions are restricted most likely to the local site of biosynthesis being dependent on the actual concentration, the duration of availability and the presence of transition metals. These findings indicate that NO may play a dual pro- and antiatherosclerotic role being dependent on local factors only.