Biomedical subjects

E Danihelová

Publications and source records attributed to E Danihelová.

15 recordsLinked to original sources

PubMed2002

Effect of H1-antagonist Dithiaden on human PMN-leukocyte aggregation and chemiluminescence is stimulus-dependent.

OBJECTIVE AND DESIGN: Contradictory data published on histamine-PMN leukocyte interactions stimulated us to study to the role of histamine and H1-antagonist Dithiaden in generation of reactive oxygen species (ROS) and aggregation of human neutrophils. METHODS AND MATERIALS: Whole blood or isolated PMN-leukocytes were exposed in a dose-dependent way to histamine or H1-antagonist Dithiaden and subsequently stimulated. Whole blood was stimulated with opsonised zymosan (OZ). Isolated cells were stimulated with membrane stimuli (OZ, N-formyl-methionyl-leucyl-phenylalanine--fMLP), or membrane bypassing stimuli (Ca2+-ionophore A23187, phorbol-myristate-acetate--PMA). The luminol-enhanced chemiluminescence (CL) was measured separately (whole blood) in a luminometer or simultaneously with neutrophil aggregation in a whole blood lumiaggregometer. RESULTS: Depending on the concentration used, Dithiaden" was 1.5- to 25.0-times more effective in inhibiting activated CL of whole blood than histamine. In isolated neutrophils both histamine and Dithiaden inhibited OZ- and A23187-stimulated CL dose-dependently, with potentiation observed after stimulation with PMA and fMLP. Histamine did not alter aggregation with any of the stimuli tested. Dithiaden inhibited A23187-, OZ- and PMA-stimulated PMN-leukocytes but potentiated fMLP-induced aggregation of isolated neutrophils. Simultaneous application of Dithiaden and histamine abolished the effect of Dithiaden on fMLP-stimulated CL. CONCLUSIONS: Dithiaden, depending on the stimuli applied, inhibited human neutrophils, both isolated or in whole blood, more markedly than histamine. The inhibition of aggregation and CL was dose- and stimulus-dependent. Histamine administered simultaneously abolished the effect of Dithiaden on fMLP-stimulated PMN-leukocytes. It seems likely that the interaction of Dithiaden with neutrophils operated both at an extra- and intracellular level.

Benzothiepins↗

PubMed2002

Antiplatelet activity of carvedilol in comparison to propranolol.

The non-selective vasodilating beta-blocker carvedilol was found to inhibit platelet aggregation as well as thromboxane B(2) formation more effectively than propranolol. The antiaggregatory activity of carvedilol decreased, depending on the stimulus used, in the following rank order of potency (in parentheses the respective mean inhibitory concentrations of carvedilol and propranolol are given in micromol/l): PMA (19 and 34) > thrombin (55 and 77) > Ca(2+)-ionophore A23187 (58 and 81) > epinephrine (86 and 118). However, aggregation of platelets activated with ADP was not affected by carvedilol in concentrations up to 100 micromol/l. In platelets stimulated with thrombin, carvedilol (10 micromol/l) reduced thromboxane B(2) formation by 64%, whereas propranolol was ineffective at this concentration. Moreover, A23187-induced formation of thromboxane B(2), not affected by propranolol, was completely blocked by 100 micromol/l carvedilol. In comparison to propranolol, the molecule of carvedilol is more lipophilic and possesses lower dipole moment and higher molar refractivity, thus penetrating into platelet membranes readily and in large quantities. The antiplatelet effect was assumed to result from interactions of carvedilol with membrane macromolecules (phospholipids, ion channels, enzymes, etc.) rather than from blockade of alpha- and beta-adrenergic receptors.

Adenosine Diphosphate↗

PubMed2000

Chloroquine: a multipotent inhibitor of human platelets in vitro.

Chloroquine inhibited human platelet aggregation in vitro both at receptor- and nonreceptor-operated stimuli. The inhibition was dose-dependent, recorded on isolated platelets as well as in platelet-rich plasma, and followed the rank order of stimuli: adrenaline (second phase)>phorbol 12-myristate 13 acetate>adenosine diphosphate>adrenaline (first phase)>thrombin>calcium ionophore A23187. In thrombin-activated platelets, chloroquine decreased in a dose-dependent manner phospholipase A(2)-induced arachidonic acid liberation from membrane phospholipids, malondialdehyde formation (a marker of membrane phospholipid peroxidation), and thromboxane generation, considered the most potent autoaggregatory agent. Chloroquine only slightly altered the arachidonic acid cascade of platelets stimulated with A23187 and phorbol 12-myristate 13 acetate. Histamine formation and liberation induced with thrombin and A23187 were not affected by chloroquine. On the other hand, thrombin-stimulated serotonin secretion was significantly decreased with chloroquine in the concentration of 10 micromol/L. This indicated that chloroquine might interfere with stimulated secretion from platelets. The results suggest that chloroquine inhibited activated platelets: first, intracellularly; second, in a close relationship to the intraplatelet Ca(2+) mobile pool; and third, most probably at the site of platelet phospholipase A(2) activation.

Adult↗

PubMed2000

Platelet-dependent modulation of polymorphonuclear leukocyte chemiluminescence.

Human blood platelets decreased luminol-enhanced chemiluminescence of human polymorphonuclear leukocytes (PMNL) stimulated with FMLP or Ca2+-ionophore A23187 by 56 or 47%, respectively. Horseradish peroxidase potentiated the decreasing effect of platelets on A23187-stimulated PMNL (92% inhibition) or reversed inhibition of FMLP-induced chemiluminescence to 94% potentiation, indicating dependence of platelet activity on availability of extracellular peroxidase. Moreover, platelet activity may depend also on the extent of platelet activation, as non-activated platelets (in the presence of FMLP) were found to potentiate PMNL-generated chemiluminescence, while platelets activated with A23187 displayed the opposite effect. Interference of platelets with formation and liberation of superoxide anion was indicated by platelet-modified isoluminol chemiluminescence. Superoxide dismutase with catalase and sodium azide were used, respectively, to differentiate the intracellular and the extracellular part of the chemiluminescence signal. Platelets were found to be capable of modifying both components of chemiluminescence, i.e., oxygen metabolites produced on the plasma membrane as well as on membranes of intracellular granules.

Adult↗

PubMed2000

Human blood platelets, PMN leukocytes and their interactions in vitro. Responses to selective and non-selective stimuli.

Using simultaneous recording of aggregation and chemiluminescence, responses of human polymorphonuclear leukocytes, blood platelets and their mixture were investigated after stimulation by specific as well as non-specific stimuli for each cell. In our experimental settings, aggregation of platelets and PMN leukocytes was increased in the following order of stimuli: PMA<A23187<thrombin and FMLP<A23187<PMA, respectively. FMLP selective for PMN leukocytes did not activate platelet aggregation, and, on the other hand, aggregation of PMN leukocytes was not induced by thrombin. The presence of PMN leukocytes decreased aggregatory responses of platelets to all the stimuli applied. Luminol amplified chemiluminescence of PMN leukocytes was increased in the order: thrombin<FMLP<A23187<PMA, but platelets alone did not show detectable chemiluminescence response to any stimulation. Platelets significantly decreased chemiluminescence of PMN leukocytes and their inhibitory effect did not depend on the type of stimulation. These observations suggest that under defined experimental conditions human PMN leukocytes and platelets might decrease mutually their dominant responses in vitro. The inhibitory effect was dependent either on the selectivity of stimuli, or on cell to cell contact before stimulus addition.

Adult↗

PubMed1999

Aggregation of human blood platelets in the presence of the pyridoindole stobadine.

The antiarrhythmic and cardioprotective drug stobadine, possessing antioxidant and neuroprotective properties, was studied as to its in vitro effect on aggregation of human blood platelets. Pretreatment of platelets with stobadine for 30 s inhibited stimulated platelet aggregation in a dose-dependent way. Depending on the aggregation stimulus used, the minimal effective concentrations of the drug were 1 micromol/l (adrenaline), 200 micromol/l (ADP), and 1,000 micromol/l (PMA). Aggregation induced with thrombin or Ca2+-ionophore A23187 was not changed in the presence of stobadine even in the concentration of 1,000 micromol/l. Addition of stobadine 30 s after adrenaline was also effective and terminated aggregation (100 and 1,000 micromol/l) or prolonged onset of its second phase (10 micromol/l). The presented experiments showed stobadine as a potent inhibitor of adrenaline-induced aggregation, indicating its involvement in the observed antithrombotic and cytoprotective activity.

Antioxidants↗

PubMed1999

Effect of stobadine on oxygen free radical generation in stimulated human polymorphonuclear leukocytes.

The generation both superoxide and a mixture of reactive oxygen species was recorded in a suspension of human polymorphonuclear leukocytes stimulated with phorbol myristate acetate. While stobadine dose-dependently decreased chemiluminescence, only its highest concentration used reduced significantly superoxide generation. The results suggest that stobadine is a more effective scavenger of free radicals rather than a quencher of superoxide anion.

Antioxidants↗

PubMed1999

Decreased arachidonic acid liberation participates in the anti-aggregatory effect of the histamine H(1)-receptor antagonist Bromadryl.

The in vitro effect of the histamine H(1)-receptor antagonist Bromadryl on aggregation of human blood platelets was studied. Bromadryl inhibited stimulated platelet aggregation in a dose-dependent way. Depending on the aggregation stimulus used, its mean inhibitory concentrations were 16 micromol/litre (thrombin), 18 micro mol/litre (A23187), 92 micromol/litre (adrenaline) and 395 micromol/litre (adenosine diphosphate). The inhibitory effect was most pronounced in aggregation stimulated with phorbol 12-myristate 13-acetate (IC(50) = 3 micromol/litre), suggesting interference of Bromadryl with protein kinase C activity. In Bromadryl-treated platelets, a very good correlation was found between aggregation and liberation of arachidonic acid; the correlation coefficients calculated for thrombin- and A23187-stimulated platelets were 0.94123 and 0.98611, respectively. This indicates that interaction of Bromadryl with phospholipase A(2) (an enzyme liberating arachidonic acid) may be involved in the anti-aggregatory effect. However, in platelets stimulated with thrombin, thromboxane formation was decreased at a lower mean inhibitory concentration of Bromadryl (6 micromol/litre) than arachidonic acid liberation (72 micromol/litre); thus, phospholipase A(2) does not seem to be the only site in the arachidonate metabolism cascade affected by Bromadryl. Although specific interference of Bromadryl with histamine receptors could not be excluded, alterations in platelet membrane structure and functions are supposed to be principal in the anti-aggregatory effect of Bromadryl.

Journal Article↗

PubMed1999

Effect of stobadine on human stimulated polymorphonuclear leukocytes.

The effect of stobadine (0.1-100 microM) on human polymorphonuclear (PMN) leukocytes stimulated with N-formyl-methionyl-leucyl-phenylalanine, a specific receptor activator, or with the calcium ionophore, A-23187 (receptor bypassing stimulus) was investigated with respect to: i) superoxide generation, ii) beta-glucuronidase release and iii) 3[H]-arachidonic acid liberation. Stobadine was found to exert an inhibitory effect on N-formyl-methionyl-leucyl-phenylalanine but not on A-23187-stimulated PMN leukocytes. The effect was more intensive on superoxide generation and beta-glucuronidase release than on 3[H]-arachidonic acid liberation. These results indicate that the inhibitory effect of stobadine is most probably via a mechanism dependent on signal transduction across the plasma membrane. This effect may occur through inhibition of arachidonate signal transduction through a regulatory G-protein.

Antioxidants↗

PubMed1996