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Biomedical subjects

P Maderna

Publications and source records attributed to P Maderna.

At least 37 records · Page 2Linked to original sources
PubMed1989

Iloprost binding and inhibition of aggregation in platelet rich plasma. Differences between normal and type IIa hypercholesterolemic subjects.

Platelets from type IIa hypercholesterolemic subjects have been previously shown to be less sensitive than normal platelets to the antiaggregatory effect of PGI2. We demonstrate here that these platelets display a reduced response to iloprost, a chemically stable analogue of PGI2, as well. In fact, the concentration of iloprost yielding 50% inhibition of PRP aggregation was higher in type IIa patients (0.77 +/- 0.08 nM) than in controls (0.51 +/- 0.06 nM, P less than 0.01). In addition, an inverse relationship existed between the threshold aggregatory concentration for collagen and the concentration of iloprost yielding 50% inhibition of PRP aggregation, both in type IIa and normal individuals. In order to elucidate the mechanism of the different sensitivity of platelets to prostacyclin and its analogue, we characterized the binding of 3H-iloprost to platelet rich plasma from single individuals. The binding was rapid, reversible, inhibited by iloprost, PGI2 and PGE1 (Kd = 50.7; 346.2 and 7500 nM, respectively); no heterogeneity of sites could be demonstrated in the PRP from a single individual. When binding studies were carried out in PRP of type IIa patients and controls, it appeared that the amount of 3H-iloprost bound at a fixed (300 nM) concentration was significantly lower in platelets from type IIa individuals (0.94 +/- 0.17 vs. 1.77 +/- 0.27 fmol/10(6) platelets, for patients and controls, respectively). It is concluded that such difference in binding might represent the mechanism underlying the reduced response to PGI2 and iloprost observed in platelets from type IIa patients.

Adult↗
PubMed1989

Albumin interferes with arachidonate metabolism in platelets and neutrophils.

The in vitro effects of albumin (150-600 microM) on arachidonate metabolism are compared in two types of circulating cells, platelets and neutrophils. The effect of this plasma protein on a functional aspect common to both these blood components, i.e. aggregation, was also investigated. Bovine serum albumin (BSA) significantly inhibited thromboxane B2 formation by washed platelets stimulated with threshold concentrations of collagen. In addition, this protein profoundly affected the formation of the major products via the lipoxygenase pathways, i.e., 12-hydroxyeicosatetraenoic acid and leukotriene B4 by platelets and neutrophils, respectively. This inhibitory effect was also confirmed for both types of cells considered on aggregation. Albumins of human origin and human plasma behaved similarly to BSA on the above parameters. Although the mechanism(s) responsible for the described effects require(s) additional studies, albumin, affecting platelet and neutrophil arachidonate metabolism, as well as the aggregatory response, might influence, in some conditions, cell activation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1988

Differential effects of oral administrations to human volunteers of acetylsalicylic acid, sodium salicylate and indomethacin on 12-hydroxyeicosatetraenoic acid formation by stimulated platelets.

The effects of single oral administrations of acetylsalicylic acid (ASA, 500 mg), indomethacin (Indo, 50 mg) and sodium salicylate (NaSal, 400 mg) on platelet aggregation and on the thromboxane B2 (TXB2) and 12-hydroxyeicosatetraenoic acid (12-HETE) synthesis by platelet rich plasma (PRP) stimulated with collagen were evaluated. While both ASA and Indo significantly inhibited TXB2 synthesis and platelet aggregation, significant reduction of 12-HETE formation at 2 and 6 h after the administration of the drug, was detected only in subjects who ingested ASA. NaSal did not affect any of the tested parameters. The comparison of the effect of ASA (200 mg) on 12-HETE synthesis in washed platelets and PRP shows that the drug is able to affect this parameter only in PRP. To obtain a constant inhibition of 12-HETE synthesis in PRP over a 24 h period, a repeated ASA treatment schedule was assessed (ASA 200 mg every 6 h for 5 times). TXB2 synthesis in PRP was almost completely suppressed at 2 h after the first ASA administration and inhibition remained constant up to 48 h after the last ASA intake. As far as 12-HETE synthesis by stimulated PRP is concerned, a significant reduction of this parameter was detected at 4 h after the first drug administration and the levels remained almost constant following the repeated administrations during a 24 h period. These data indicate that ASA, but not Indo and NaSal, significantly affect not only TXB2 synthesis but also 12-HETE formation in PRP. The lack of the effect of ASA administration on 12-HETE, found when studies were carried out in washed platelets, indicates that the drug requires the presence of plasma factors for its activity on the formation of 12-lipoxygenase products by platelets.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1988

Vitamin E influences the effects of fish oil on fatty acids and eicosanoid production in plasma and circulating cells in the rat.

An EPA enriched oil (MaxEPA, Seven Seas, U.K. containing 18% EPA and 12% DHA) alone or supplemented with 10 mg/ml/alpha tocopherol, was administered by gastric intubation at the dose of 3.2 ml/kg/day for a period of eight weeks to male rats fed a standard diet. An additional group of animals was treated with the same amount of olive oil. The administration of MaxEPA alone resulted, as expected, in accumulation of EPA and reduction of AA levels in plasma, platelet, red blood cell and PMNL phospholipids, when compared to values in the olive oil group. In addition, levels of linoleic acid were elevated, suggesting inhibition of the conversion of linoleic to arachidonic acid. Formation of i.r. TxB2 by stimulated PRP, of i.r. 6-keto-PGF1 alpha by perfused aortas, and of IR LTB4 and C4 by stimulated PMNL were reduced, but production of superoxide anion by PMNL was enhanced by MaxEPA treatment vs the olive oil treatment. Supplementation of MaxEPA with vitamin E caused a smaller reduction of 20:4 levels and a smaller increase of 20:5 levels in plasma and cell phospholipids and modified the effects of MaxEPA on eicosanoid and superoxide anion production, suggesting that lipid peroxidation may mediate some of the biological effects of omega 3 fatty acids.

Animals↗
PubMed1987

Indobufen is a potent inhibitor of whole blood aggregation in patients with a high atherosclerotic risk.

The newly developed method, based on the quantitation of changes in electrical impedance, to determine platelet aggregation in whole blood was applied to the evaluation of the effects of Indobufen, a well known inhibitor of platelet rich plasma aggregation. The platelet antiaggregatory activity of the drug after single (200 or 400 mg) and repeated doses (200 mg or 200 mg b.i.d. for 1 week) was determined on whole blood aggregation and thromboxane B2 formation by platelet rich plasma of 16 patients with high risk of atherosclerosis. At 2 hr after the single dose treatments, Indobufen significantly reduced the whole blood aggregation induced by 0.5-2 micrograms/ml collagen. At 24 hr from the intake of the drug the aggregation was significantly inhibited in patients who ingested the 400 mg dose only. As far as the repeated administrations are concerned, it appears that the inhibition of whole blood aggregation and thromboxane B2 formation by platelets reached 12 hr after the last drug administration was comparable to the degree of inhibition achieved 2 hr after Indobufen intake. It is concluded that Indobufen orally administered to patients with high risk of atherosclerosis is a potent inhibitor of whole blood aggregation.

Adult↗
PubMed1987

Effects of gemfibrozil on plasma lipoprotein-apolipoprotein distribution and platelet reactivity in patients with hypertriglyceridemia.

The effects of gemfibrozil on plasma lipoprotein distribution and composition and on platelet function were investigated in 11 patients with stable hypertriglyceridemia, six belonging to Fredrickson type IIb and five to type IV. Gemfibrozil (600 mg twice a day) significantly reduced total and very low density lipoprotein (VLDL)--associated triglyceridemia (respectively-32.4% and -40.4%, after 6 weeks of treatment). No significant variations were noted in the lipid components of low-density lipoproteins; by contrast, a marked increase (18%) was detected in high-density lipoprotein (HDL)--associated cholesterol. Comparison of the two patient groups (type IIb and type IV) showed that those with type IIb had both a more significant reduction of triglyceridemia and a more marked increase of HDL-cholesterol. Apolipoprotein B levels were reduced in both groups (-12%) with no change in apolipoprotein AI. The cholesterol content in the HDL subfractions, separated by rate zonal ultracentrifugation, was raised in HDL3 (18%) and in HDL2 (14%). Both particles also showed significant increases of the cholesterol/protein and the cholesterol/phospholipid ratios. A non-statistically significant decrease in collagen-induced aggregation and in the release of thromboxane B2 was noted after treatment. These findings suggest that, similar to what was recently reported in normal individuals and in laboratory animals, the probable mode of action of gemfibrozil is in reducing the secretion of atherogenic lipoproteins, particularly VLDL, while stimulating the production of small HDL particles.

Adult↗
PubMed1986

Dietary interventions in north Karelia, Finland and south Italy. Modification of thromboxane B2 formation in platelets of male subjects only.

The effects of dietary interventions, based on changes of total fat, saturated fatty acids and cholesterol contents and of the polyunsaturated/saturated (P/S) fatty acid ratio of the diet, were studied in normal male and female subjects, living in North Karelia, Finland, and South Italy. In North Karelia the increase of P/S ratio (from 0.15 to 1.2) of the diet for a 6-week period resulted in reduced thromboxane B2 (TxB2) production by collagen-stimulated platelets only in male subjects, whereas plasma total, LDL and HDL cholesterol were reduced in both sexes. After a 6-week return to the original diet, plasma lipid levels were restored in all subjects. In the South Italy study, changes in platelet TxB2 production were observed only after return to the original diet in male subjects. Total and LDL cholesterol were significantly increased during the dietary intervention and returned toward baseline levels after switch back to the original diet. These data indicate that the increase of the P/S ratio in the diet reduces platelet TxB2 formation only in men.

Adult↗
PubMed1986

In vitro effects of aspirin and non steroidal anti-inflammatory drugs on the formation of 12-hydroxyeicosatetraenoic acid by platelets.

The in vitro effects of aspirin and other non steroidal antiinflammatory drugs (NSAIDs) on 12-HETE formation were evaluated in platelet rich plasma (PRP) stimulated with collagen. Aspirin (1 X 10(-4)-1 X 10(-3) M) inhibited 12-HETE production in PRP. Inhibition of 12-HETE formation was detected also in PRP incubated with indomethacin and BW 755C. Sodium salicylate, instead, did not reduce 12-HETE synthesis. Aspirin (3 X 10(-3) M) did not modify 12-HETE synthesis in similarly challenged washed platelet (WP) preparations, inspite of its effect on the cyclooxygenase pathway. It may be concluded that aspirin and other NSAIDs, not only affect the cyclooxygenase pathway, but also inhibit 12-HETE synthesis. In addition it is shown that the 12-HETE synthesis is reduced by plasma and that this effect is enhanced in the presence of aspirin.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1986

Controlled evaluation of fat intake in the Mediterranean diet: comparative activities of olive oil and corn oil on plasma lipids and platelets in high-risk patients.

Activities of low-fat diets with olive oil or corn oil on lipids and platelets were studied in 23 middle-aged patients with high atherosclerosis risk for 8 wk. The olive oil diet had a polyunsaturated-saturated ratio of 0.33 vs 1.28 for the corn oil diet. Plasma total cholesterol was reduced with corn oil, but high-density lipoprotein cholesterol levels were lower with corn oil and unchanged or raised by olive. Plasma apolipoprotein B levels were equally reduced by both diets; apolipoprotein AI and the apo AI:B ratio rose only with olive oil. Plasma-glucose levels were lowered significantly with olive oil. Changes in platelet function were characterized by a reduced sensitivity to arachidonic acid (particularly with corn oil) and to collagen (particularly with olive). An olive oil diet with a moderate fat intake (about 30% of total calories) leads to favorable plasma lipoprotein and platelet changes.

Adult↗
PubMed1986

Aspirin inhibits platelet 12-hydroxy-eicosatetraenoic acid formation.

The effects of aspirin on platelet 12-hydroxyeicosatetraenoic acid (12-HETE) formation were studied after administration to humans in platelet-rich plasma (PRP) and in vitro in human PRP and in washed platelets (WPs). Healthy volunteers were given orally either single or repeated (1 week) daily doses (20 and 500 mg) of aspirin. Two hours after a single 20 mg aspirin dose, 12-HETE formation by PRP was significantly inhibited. With the highest aspirin dose used (500 mg), the inhibition of 12-HETE formation was more pronounced and long lasting. Thromboxane B2 (TXB2) synthesis was significantly inhibited at 2 hours with the lowest dose. At the 500 mg dose, platelet aggregation was significantly reduced, and TXB2 formation was almost completely suppressed for at least 24 hours. The degree of inhibition of 12-HETE formation at 2 hours after 1 week of daily treatment (20 and 500 mg) was similar to that achieved at 2 hours after the single dose. As far as TXB2 and platelet aggregation are concerned, the effect of 20 mg aspirin was cumulative. In vitro studies show that aspirin (0.25 to 3 mmol/L concentration) significantly inhibits 12-HETE formation in PRP, but not in WPs, suggesting that plasma is required for the aspirin effect on lipoxygenase products. These results indicate that aspirin, even at low doses, not only affects the platelet cyclooxygenase activity but also exerts reversible inhibition of 12-HETE formation, both in vitro and ex vivo. These data may help to further elucidate the role of hydroxyacids in the anti-inflammatory and antipyretic action of aspirin.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1985

Prostacyclin-lipoprotein interactions. Studies on human platelet aggregation and adenylate cyclase.

The in vitro effects of different lipoprotein fractions (VLDL, LDL and HDL) on human washed platelet aggregation, induced by collagen and thrombin, were evaluated in the presence and absence of PGI2. Although VLDL and LDL increased the platelet aggregation while HDL showed an opposite effect, none of the tested lipoprotein fractions affected the potency of PGI2 as inhibitor of platelet aggregation (IC50). In addition, studies were performed to evaluate the effects of lipoproteins on adenylate cyclase activity in human platelet membranes. The three lipoprotein classes inhibited both basal and PGI2-stimulated adenylate cyclase without affecting the EC50 for PGI2. This inhibitory activity was not specifically elicited by any protein or lipid since neither bovine serum albumin nor a lipid emulsion (Intralipid) displayed any inhibition. The effect on adenylate cyclase elicited by VLDL, LDL and HDL does not seem to be correlated with the activity on platelet aggregation. It is concluded that mediators other than cAMP might be involved in the control of platelet function by lipoproteins.

Adenylyl Cyclases↗
PubMed1985

Oral polyunsaturated phosphatidylcholine reduces platelet lipid and cholesterol contents in healthy volunteers.

The effects of orally administered polyunsaturated phosphatidylcholine (PPC) on plasma lipids, lipoproteins and platelet function and composition were studied in seven healthy male volunteers. PPC (Nattermann & Cie, GmbH, Cologne, Federal Republic of Germany), 10 g/day, was given for a 6-week period after a 4-week wash out; laboratory tests were repeated after a further 4-week period after the end of treatment. PPC did not appear, during treatment, to modify the levels of plasma total cholesterol and triglycerides. High density lipoprotein (HDL) cholesterol levels were, however, increased after six weeks of PPC. The most dramatic changes occurred in platelet membrane composition: the total lipid/total protein and the cholesterol/protein ratios were reduced significantly, whereas increases of the phospholipid/total lipid ratio and of the linoleic acid membrane content were observed. Platelet function tests, both in whole blood and in platelet rich plasma, were not modified. Similarly, the thromboxane B2 formation after standard stimuli and the sensitivity to exogenous prostaglandin I2 also were unchanged. During the final wash out period following treatment, a reduction of plasma total and low density lipoprotein (LDL) cholesterol levels also was recorded. PPC appears to be capable of modulating lipid exchanges between cell membranes and the plasma compartment.

Administration, Oral↗
PubMed1985

Plasma lipoproteins affect platelet malondialdehyde and thromboxane B2 production.

Platelet interaction with plasma lipoproteins was studied using gel-filtered platelets free of plasma constituents and purified lipoproteins. On incubation of gel-filtered platelets with plasma lipoproteins at 30 degrees C for 30 min, 100 micrograms of protein/ml of very-low as well as low-density lipoprotein caused 10% increment in platelet aggregation and [14C]serotonin release in parallel to elevation of around 15% of malondialdehyde and thromboxane B2 production. High-density lipoprotein showed the opposite effect and reduced platelet aggregation as well as thromboxane B2 synthesis by 17 and 32%, respectively. Lipoprotein-deficient plasma enhanced platelet function. Preincubation of the platelet suspension with prostacyclin did not prevent the effect of the lipoproteins on the in vitro platelet response as well as on the platelet prostaglandin pathway. Our results suggest that the formation of thromboxane B2 and malondialdehyde is influenced by plasma lipoproteins and that these, in turn, affect platelet aggregation and the release reaction. The possible significance of these results to platelet function in hyperlipidemic patients is discussed.

Blood Platelets↗
PubMed1985

Differential effects of aspirin and indomethacin on platelet and leukocyte thromboxane A2 formation.

In this study, the in vitro inhibitory effects of aspirin and indomethacin on the arachidonic acid induced thromboxane B2 formation by human leukocytes, are evaluated. The results are compared to those obtained using similarly challenged human washed platelets. Acetylsalicylic acid inhibition, calculated as IC50 by a dose-response curve, is more than ten fold higher for leukocytes vs platelets. In fact, a concentration of aspirin as low as 5 microM almost completely suppresses thromboxane B2 formation by washed platelets, whereas a concentration of 50 microM is necessary to achieve the same inhibition with leukocytes. Indomethacin (0.001-100 microM), incubated with platelet and leukocyte suspensions acts similarly to aspirin. Leukocyte and platelet cyclooxygenases are, therefore, differently affected by both aspirin and indomethacin. These differences may be relevant in the understanding of the wide divergence between the aspirin doses used in thrombosis prevention and in the treatment of inflammatory disease.

Aspirin↗
PubMed1985

Pathological significance of the thromboxane-prostacyclin hypothesis.

Disturbances in the balance between the production of thromboxane A2 by the platelets and that of prostacyclin by the vessel wall may play a major role in disease and be a target for therapeutic agents. Acetylsalicylic acid, given in small doses, may inhibit the production of thromboxane A2 without affecting that of prostacyclin. Even if it reduces prostacyclin synthesis, the drug is beneficial as an antithrombotic agent, possibly because it has actions not related to inhibition of cyclooxygenase. Dazoxiben not only inhibits the production of thromboxane A2 by platelets, but also facilitates that of prostanoids, in part by diverting endoperoxides to the blood vessel wall and to leukocytes. Although reduced production of prostacyclin may contribute to the etiology of atherosclerosis, the blood vessel wall of hypercholesterolemic animals exhibits an increased production of prostacyclin. The latter has been given successfully in patients with accelerated turnover of platelets or with peripheral vascular disease. However, its very short t1/2 limits its practical use. The availability of stable prostacyclin derivates, such as ZK 36374, may bypass this problem.

Animals↗
PubMed1985

Control of human and animal platelet aggregation by a new prostacyclin analog.

The in vitro effects of ZK 36 374, a new chemically stable prostacyclin (PGI2) analog, on platelet aggregation were studied and compared to those of PGI2. Significantly lower concentrations of ZK 36 374, versus prostacyclin, were required to inhibit collagen and epinephrine-induced aggregation in human platelet-rich plasma. In contrast, in rat and rabbit platelet rich plasma, PGI2 was more effective than ZK 36 374 in inhibiting the aggregation elicited by ADP and collagen. It is concluded that ZK 36 374 is a potent antiaggregatory compound and may be useful in the prevention of cardiovascular disorders.

Adenosine Diphosphate↗