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Biomedical subjects

C Cerletti

Publications and source records attributed to C Cerletti.

At least 73 records · Page 4Linked to original sources
PubMed1991

Platelet activation by fMLP-stimulated polymorphonuclear leukocytes: the activity of cathepsin G is not prevented by antiproteinases.

Human polymorphonuclear leukocytes (PMN) activated by fMLP (in the presence of CaCl2, fibrinogen, and cytochalasin B) were able to induce aggregation, cytoplasmic Ca2+ increase, and thromboxane A2 production in coincubated autologousplatelets. Cell-free supernatants prepared from n-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated PMN were able also to induce platelet activation. Antibodies against cathepsin G and different serin protease inhibitors completely suppressed the activity of PMN-derived supernatants, indicating that cathepsin G is the major platelet activator released by PMN in our system. However, antiproteinases only partially affected platelet activation induced by PMN in mixed cell suspensions. Superoxide dismutase and catalase added to the cell suspension did not affect platelet activation nor potentiated serin protease inhibitors, making a role for short-lived oxygen radicals in our experimental system unlikely. Electron microscopic observation of stirred mixed cell suspensions preincubated for 2 minutes at 37 degrees C before stimulation showed a close PMN-platelets contact without any morphologic or biochemical event suggesting platelet activation. Preincubation of the cells without stirring to minimize PMN-platelet interaction before stimulation did not modify subsequent aggregation and platelet cytoplasmic Ca2+ increase in control samples. However, in this condition trypsin inhibitor from soybean completely prevented PMN-induced platelet activation. In samples preincubated without stirring in the presence of the antiproteinase, activated PMN stuck together but platelets preserved their discoid shape and did not appear significantly activated. We propose that membrane-to-membrane contact could create a microenvironment in which cathepsin G, discharged from stimulated PMN on adherent platelets, is protected from antiproteinases.

Blood Platelets↗
PubMed1990

Coagulation, fibrinolytic and platelet function in patients on long-term therapy with aspirin 300 mg or 1,200 mg daily compared with placebo.

Aspirin has been shown to be beneficial in the prophylaxis of arterial thromboembolic disease. The rationale for its use as an antithrombotic drug lies in its inhibition of thromboxane A2-dependent platelet function. However, the effect of aspirin on coagulation and fibrinolysis during chronic therapy has not been studied. We have measured a range of haemostatic and platelet functions in 49 patients with transient ischaemic attacks randomly allocated to aspirin 300 mg a day, aspirin 1,200 mg a day or placebo. All had been taking their allocated treatment for between 9 months and 4 years prior to investigation. Bleeding time was prolonged, serum thromboxane diminished and platelet aggregation to arachidonic acid but not ADP was abolished by both 300 mg and 1,200 mg aspirin, in a non-dose dependent fashion. Serum salicylate increased with the dose of aspirin ingested. No effect was seen with either dose of aspirin on urinary thromboxane and 6-keto-PGF1 alpha excretion, or on coagulation. Patients taking 1,200 mg aspirin a day had a lower haemoglobin and packed cell volume, lower resting fibrinopeptide A concentration and lower basal plasminogen activator activity than those on placebo. Response to venous occlusion was normal in all groups. The results suggest 300 mg and 1,200 mg aspirin have an equivalent platelet inhibitory effect but 1,200 mg aspirin causes greater gastro-intestinal blood loss.

Aged↗
PubMed1990

The (+)-enantiomer is responsible for the antiplatelet and anti-inflammatory activity of (+/-)-indobufen.

The racemic compound indobufen and its (+)- and (-)-enantiomers have been compared for their effects on blood platelet function and rat carrageenan pleurisy. The antiplatelet properties were studied in-vitro in human platelets by measuring the inhibition of platelet aggregation and generation of serum thromboxane (Tx) B2. In-vivo, the antiplatelet and anti-inflammatory properties were studied in rats by measuring the inhibition of serum TxB2, the amount of 6-keto-PGF1 alpha in pleural exudate and pleural exudate volume. In all tests the (+)-enantiomer was slightly more potent than the racemate, while the (-)-enantiomer was far less potent. In the same rats, treatment with the lowest doses of the compounds giving 90% inhibition of serum thromboxane B2 generation was associated with occasional macroscopic lesions of the gastric mucosa.

Animals↗
PubMed1990

Platelet activation by polymorphonuclear leukocytes exposed to chemotactic agents.

Human platelets were loaded with aequorin, a Ca2(+)-sensitive photoprotein, and tested in the platelet-ionized calcium aggregometer for simultaneous recording of platelet aggregation and intraplatelet Ca2+ levels both in the presence and in the absence of autologous polymorphonuclear leukocytes. Cells were exposed to one of three chemotactic stimuli: platelet-activating factor (PAF), N-formyl-methionyl-leucyl-phenylalanine (FMLP), or leukotriene B4 (LTB4). Platelets alone aggregated and showed intracellular Ca2+ movement only when exposed to PAF. Amplification of both platelet aggregation and intraplatelet Ca2+ movement was induced by PAF in the presence of leukocytes. Aggregation and intraplatelet Ca2+ mobilization were also observed in the presence of leukocytes activated by either FMLP or LTB4. Both parameters increased with the concentration of the stimuli and/or the number of leukocytes. Platelet thromboxane B2 production was also significantly increased in the presence of leukocytes. Addition of platelets at different times after leukocyte activation resulted in progressively reduced cytoplasmic Ca2+ increase. Cell-free supernatants prepared from FMLP-stimulated leukocytes were able to induce platelet aggregation, thromboxane B2 generation, and Ca2+ mobilization, although at a reduced degree as compared with intact leukocyte addition. The activity of leukocyte supernatants was stable at 37 degrees C for up to 30 min and was suppressed by trypsin inhibitor. Our study indicates that stimulated leukocytes release a soluble enzymatic activity able to activate platelets; cell-to-cell interaction may also play a role in this phenomenon. Platelet-leukocyte interaction could have physiopathological relevance and constitutes a new model for studying old and new platelet inhibitory drugs.

Blood Platelets↗
PubMed1990

Interaction of prostaglandins and the myogenic factor in the mechanism of closure of the ductus arteriosus.

Although the role of prostaglandins (PG) in the mechanism of dilatation of the ductus arteriosus (DA) has received considerable attention, no data on their possible interaction with the pressure-induced myogenic reaction are available. There is also a lack of information on PG production by the foetal blood vessels of the guinea-pig, in which the DA closes rapidly. Use of the RIA method showed relatively low PG production by isolated foetal guinea pig blood vessels, as represented by the main products, PGI1 and PGE2. When computed in pmol per mg wet weight, the production of 6-keto-PGF1 alpha (an equivalent of PGI2) was statistically significantly higher in the foetal DA (4.06 +/- 1.13) than in the foetal aorta (2.04 +/- 0.33). The isolated DA reacts to a sudden increase in perfusion pressure by marked constriction, which in some cases leads to functional closure of the DA. In 10(-7) to 10(-5) mol.l-1 concentration, PGE2 reversibly inhibits pressure-induced myogenic constriction, while under the same conditions the contractility of the DA in response to oxygen is unaffected. In concentrations of 10(-6)-10(-5) mol.l-1, indomethacin, a blocker of PG biosynthesis, also induces pressure constriction and it raises the basal flow resistance of isolated DA preparations. The results indicate that PGs play a modulator role in the pressure myogenic response of the DA of guinea-pig and rabbit foetuses.

Animals↗
PubMed1989

The blood platelet as an inflammatory cell.

Platelets seem to be involved in inflammatory responses. They release substances which can cause vasodilation or vasoconstriction. Platelet Derived Growth Factor (PDGF) induces monocyte accumulation and activation and there is evidence that some mediators released from these cells can affect neutrophil migration as well as function. Furthermore, platelet derived cytokines participate in the processes of tissue repair, particularly fibroblast proliferation and matrix remodelling. We review some of the possible mechanisms which have been proposed to explain this role of platelets in the appearance and persistence of inflammatory reactions at the tissue sites.

Blood Platelets↗
PubMed1988

Moderate anticoagulation by salicylate prevents thrombosis without bleeding complications. An experimental study in rats.

It has previously been shown that salicylate (S) acts as a vitamin K (vit K)-antagonist inducing a decrease in plasma levels of vit K-dependent clotting factors and inhibiting the vit K-dependent carboxylation reaction in the liver. In this study we evaluated whether this biochemical effect had a possible functional role. Indeed, we tested in rats the antithrombotic potency of S (175 mg/kg/i.p. twice a day for 3 days) on experimentally induced venous thrombosis. Its possible haemorrhagic effect was evaluated by measuring the bleeding time. Low-dose warfarin (W) (0.2, 0.1, 0.1 mg/kg/i.v. for 3 days) was utilized as control drug. To check for a possible potentiation between S and W, we tested the effects of their combination (S + W). Thrombotest was used to monitor the anticoagulant effect of each treatment. The incidence of thrombus formation, after venous stasis, was not significantly affected by any of the treatments used, but a significant reduction in thrombus weight was observed after either S or W treatment. Both drugs partially prolonged the Thrombotest without affecting either the bleeding time or the peri-operative mortality (mainly due to internal bleeding). When the combination S + W was used, no significant benefit was observed on the prevention of thrombus incidence or weight, although a marked Thrombotest prolongation was recorded. On the other hand this combination resulted in a pronounced bleeding tendency, as expressed in a significant prolongation of bleeding time and increased total mortality. Thus S, at doses inducing moderate anticoagulation may prevent venous thrombosis without relevant bleeding complications.

Animals↗
PubMed1988

Phospholipase C from clostridium perfringens induces human platelet aggregation in plasma.

We studied the aggregating effect of different concentrations of phospholipase C (PLC) (extracted from Clostridium perfringens) on human platelet-rich plasma (PRP). PRP was preincubated with PLC for 3 min at 37 degrees C and the platelet aggregation was followed for 10 min. The threshold aggregating concentration (TAC) of PLC was 3-4 U/ml. We also studied the potentiation of PLC with other stimuli on platelet aggregation. Potentiating stimuli, such as arachidonic acid (AA), ADP. Platelet Activating Factor (PAF) and U-46619 (a stable analogue of cyclic endoperoxides) were all used at subthreshold concentrations. We also studied the possible inhibitory effect of aspirin, apyrase, TMQ, a prostaglandin endoperoxide/thromboxane receptor antagonist and BN-52021, a PAF receptor antagonist. Only aspirin and apyrase were able to reduce aggregation induced by PLC alone and PLC + AA and PLC + ADP respectively. TMQ and BN-52021 were inactive. In ex vivo experiments oral aspirin (500 mg) partially inhibited platelet aggregation induced by PLC alone, PLC + AA and PLC + ADP 2 and 24 h after administration. Aspirin 20 mg for 7 days also reduced aggregation induced by PLC + AA.

Adenosine Diphosphate↗
PubMed1988

A new model of pulmonary microembolism in the mouse.

The method of infusion of hardened red blood cells described by Clement et al. (1983) to induce pulmonary hypertension in the minipig has been modified to obtain a model of pulmonary microembolism in the mouse. In this model, the infusion of hardened red blood cells causes the death of about 90% of control animals in 2-5 min, and the efficacy of a given pharmacological treatment can be assessed in terms of the percentage of animals protected from death 15 min after the infusion. Platelets are not apparently involved, since the number of circulating platelets, plasma levels of TxB2, and PF-4 are not modified, and the mortality in thrombocytopenic animals is not different from controls. Furthermore, aspirin and heparin are totally inactive in this model. Preliminary results with some Ca++ channel blockers (nitrendipine and nicardipine) indicate that these compounds may be active. This experimental model offers an easy and relatively inexpensive test for the characterization of compounds to prevent pulmonary microembolism, acting via a platelet-independent mechanism.

Animals↗
PubMed1988

Inhibition of thromboxane biosynthesis by 3-pyridinol carboxypentyl ethers substituted with a hydroxylated octyl chain.

Racemic 6-[4-(3'-hydroxy-1'-octenyl)-3-pyridyloxy]hexanoic and 6-[4-(3'-hydroxyoctyl)-3-pyridyloxy] exanoic acids have been synthesized and their activity as inhibitors of the biosynthesis of thromboxane A2 in human serum has been studied, in comparison with isomers having the eight-carbon chain in the 2 position. Very high, selective activity was found for the new 4-substituted 3-pyridinol ethers, whereas the 2-substituted compounds showed no action.

Depression, Chemical↗
PubMed1988

Selectivity of oral aspirin as an inhibitor of platelet vs. vascular cyclooxygenase activity is reduced by portacaval shunt in rats.

Oral aspirin can be extensively hydrolyzed to salicylate in the stomach and liver before it enters the systemic circulation. "Presystemic" acetylation of platelets may thus occur during aspirin absorption. This may result in concomitant sparing of peripheral vascular cyclooxygenase mainly exposed to salicylate. We tested whether the "biochemical selectivity" of p.o. aspirin as an inhibitor of platelet rather than vascular cyclooxygenase was reduced by elimination of the "first-pass" hepatic metabolism. A portacaval shunt was inserted in anesthetized rats by connecting the portal vein to the inferior vena cava through a heparinized polyethylene "Y" cannula. Sham-operated rats acted as controls. Ninety minutes after recovery from anesthesia rats were given aspirin p.o. (10 mg/kg) and 45 min later serum thromboxane B2 and 6-keto-prostaglandin F1 alpha formation by vascular rings was evaluated by radioimmunoassay. Serum thromboxane B2 was almost suppressed completely in all animals; vascular 6-ketoprostaglandin F1 alpha was reduced significantly (by 40-60% in aorta and vena cava) in rats with the portacaval shunt but not in sham-operated animals. The results in rats with the shunt were similar to those obtained previously after i.v. aspirin. Fifteen minutes after aspirin, plasma levels of unmetabolized drug measured by high-pressure liquid chromatography were significantly higher in rats with portacaval shunt (0.56 +/- 0.16 micrograms/ml; n = 5) than in sham-operated controls (0.16 +/- 0.02 micrograms/ml; n = 5). These findings support directly the role of first-pass hepatic metabolism in the "biochemical selectivity" of p.o. aspirin.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Response of human platelets exposed to arachidonate upon stimulation with other agonists: possible role of Ca2+i movement.

Arachidonate (25 microM) induced only 20% maximal platelet aggregation but 80% maximal cytoplasmic ionized calcium movement (as measured by the photoprotein aequorin). Preincubation with 25 microM arachidonate prevented platelet aggregation and cytoplasmic ionized calcium movement induced by threshold concentrations of the thromboxane A2 analogue U-46619, but did not prevent platelet aggregation induced by threshold concentrations of thrombin, despite a marked reduction of cytoplasmic ionized calcium movement. These findings suggest that thrombin may employ pools of cytoplasmic ionized calcium and/or mechanisms to mobilize it different from those utilized by arachidonate and its metabolites.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1987

Pharmacokinetics of enteric-coated aspirin and inhibition of platelet thromboxane A2 and vascular prostacyclin generation in humans.

We evaluated whether an enteric-coated aspirin formulation showed a "presystemic" component in its antiplatelet effect and if so would spare vascular cyclooxygenase. In six healthy volunteers, 30 to 45 minutes after ingestion of 325 mg enteric-coated aspirin, platelet thromboxane A2 generation was inhibited by about 20% before any drug could be detected in the peripheral venous blood. A further decline in thromboxane A2 generation occurred with appearance of aspirin in blood between 60 and 240 minutes. No presystemic component could be detected after 325 mg aspirin tablets. Ten patients undergoing saphenectomy received 325 mg of either aspirin tablet or enteric-coated aspirin; 12 hours later platelet thromboxane A2 and peripheral vascular prostacyclin generation were significantly reduced by 98% and 58%, respectively. The effects of the two aspirin formulations were not different. Aspirin formulations with "presystemic" component in their antiplatelet effect may not necessarily result in sparing of peripheral vascular cyclooxygenase.

Adult↗
PubMed1987

Effects of sulfinpyrazone and its metabolite G25671 on platelet activation and desensitization and on bronchoconstriction induced by the prostaglandin endoperoxide analog U46619.

Sulfinpyrazone (100 microM) and its thioether metabolite G25671 (50 microM) suppressed arachidonic acid-induced platelet aggregation, thromboxane (Tx) B2 formation and ATP release. Platelet activation by the endoperoxide analog U46619 also was prevented by sulfinpyrazone or G25671 (0.3-1 mM). Previous studies have shown that human platelets pre-exposed to arachidonic acid or to U46619 and then washed and resuspended failed to respond to a second challenge by both arachidonic acid and U46619; desensitization by arachidonic acid and U46619 occurred at a site sensitive to endoperoxides/Tx receptor antagonists; and the desensitizing effects of U46619 were direct, whereas those of arachidonic acid were mediated by a cyclooxygenase-dependent metabolite. We now demonstrate that the presence of sulfinpyrazone or G25671 during platelet exposure to arachidonic acid or U46619 prevented desensitization. We also studied the threshold aggregating concentration of arachidonic acid and U46619 in healthy subjects before and after treatment with sulfinpyrazone and we found a good correlation between ex vivo and in vitro findings. We finally examined the actions of sulfinpyrazone and G25671 on the bronchoconstriction in vivo and parenchymal lung strip contraction in vitro induced by U46619. Neither drug had any preventive effect. Our results demonstrate that sulfinpyrazone and its metabolite G25671 are not only cyclooxygenase inhibitors but can also act as endoperoxide/Tx antagonists and indicate clearly that antagonism of U46619 by both drugs is selective for platelets.

Arachidonic Acid↗