The human platelet as a reproducible and sensitive cell for the detection and assay of platelet-activating factor

Ekholm, Janice E.; Tatsumi, Yoshio; Nouchi, T.; Hanahan, Donald J.

doi:10.1016/0003-2697(92)90142-t

Cited by 9 publications

(4 citation statements)

References 16 publications

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“…Responses of washed human platelets to LPAs were stable, when the platelets were incubated with a threshold concentration of ADP (10 µM) in the presence of fibrinogen and Ca# + , as previously reported [28,36]. The potencies of aggregating activities of 1-20 : 4-, 1-20 : 5-and 1-22 : 6-LPAs towards washed human platelets were compared with those of other 1-acyl-and 1-O-alkyl-LPAs.…”

Section: Platelet-aggregating Activities Of 1-highly Unsaturated Acylsupporting

confidence: 53%

“…13 ml aliquots of anticoagulated blood were transferred to plastic tubes, and centrifuged at 830 g for 10 min at room temperature. Platelet-rich plasma was recovered, and platelets were isolated essentially as described in [36]. In brief, platelets were separated from plasma components by centrifugation at 1000 g for 15 min, and resultant pellets were washed twice with Tyrode-Hepes buffer with no Ca# + (pH 6.5 ; 137 mM NaCl, 2.6 mM KCl, 12.0 mM NaHCO $ , 0.42 mM NaH # PO % , 1.0 mM MgCl # , 5.0 mM Hepes and 0.56 mM glucose) containing 10 µM adenosine.…”

Section: Measurement Of Platelet Aggregationmentioning

confidence: 99%

“…Then, the platelet-rich plasma was centrifuged twice, and four-fifths of the supernatant was withdrawn for the next centrifugation to reduce the numbers of contaminating erythrocytes and leucocytes. Finally, one more washing of the isolated platelets was added to the procedure described previously [36].…”

Section: Detection Of Mrnas Encoding Edg-2 Edg-4 and Edg-7 By Reversmentioning

confidence: 99%

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Human platelets respond differentially to lysophosphatidic acids having a highly unsaturated fatty acyl group and alkyl ether-linked lysophosphatidic acids

Tokumura

Sinomiya

Kishimoto

et al. 2002

Biochemical Journal

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Lysophosphatidic acid (LPA) is a physiological agonist that is produced by lysophospholipase D, phospholipase A(1) and phospholipase A(2) in the blood of animals. It exerts diverse biological actions on a broad range of animal cells. Specific receptors for this important agonist have been characterized. In this investigation, for the first time we prepared LPAs having a highly unsaturated fatty acyl group, such as the eicosapentaenoyl or docosahexaenoyl residue, and their acetylated derivatives. Human platelets aggregated more potently in response to the highly unsaturated acyl-LPAs than to LPAs with a C(18) fatty acyl group, such as an oleoyl group, while alkyl ether-linked LPAs (alkyl-LPA) had much stronger aggregating activity. Two positional isomers of LPAs with an arachidonoyl, eicosapentaenoyl or docosahexaenoyl group had equipotent aggregatory activity as well as the positional isomers of their acetylated analogues, indicating that putative LPA receptors could not distinguish the difference between the positional isomers. We found that platelet preparations from two individuals showed no aggregatory response to alkyl-LPAs, although they contained mRNAs for known LPA receptors in the following order of expression level: endothelial differentiation gene (Edg)-4>Edg-7>Edg-2. We also obtained evidence that 2-(p-amylcinnamoyl)amino-4-chlorobenzoic acid (ONO-RS-082), a phospholipase A(2) inhibitor, potentiated alkyl-LPA-induced platelet aggregation, but inhibited highly unsaturated acyl-LPA-induced platelet aggregation. These results indicated that human platelets express acyl-LPA-selective and alkyl-LPA-selective receptors on their plasma membrane.

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Section: Platelet-aggregating Activities Of 1-highly Unsaturated Acylsupporting

confidence: 53%

Section: Measurement Of Platelet Aggregationmentioning

confidence: 99%

Section: Detection Of Mrnas Encoding Edg-2 Edg-4 and Edg-7 By Reversmentioning

confidence: 99%

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Human platelets respond differentially to lysophosphatidic acids having a highly unsaturated fatty acyl group and alkyl ether-linked lysophosphatidic acids

Tokumura

Sinomiya

Kishimoto

et al. 2002

Biochemical Journal

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“…LPA generation does not seem to play any role in either the activation or the desensitization process. Our studies showed only a weak aggregatory effect of LPA, which differs from a recent report [18] but agrees with other studies [34,38].…”

Section: Discussionsupporting

confidence: 87%

Human group II 14 kDa phospholipase A2 activates human platelets

Polgár

Kramer

et al. 1997

Biochemical Journal

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Recombinant human group II phospholipase A2 (sPLA2) added to human platelets in the low microg/ml range induced platelet activation, as demonstrated by measurement of platelet aggregation, thromboxane A2 generation and influx of intracellular free Ca2+ concentration and by detection of time-dependent tyrosine phosphorylation of platelet proteins. The presence of Ca2+ at low millimolar concentrations is a prerequisite for the activation of platelets by sPLA2. Mg2+ cannot replace Ca2+. Mg2+, given in addition to the necessary Ca2+, inhibits sPLA2-induced platelet activation. Pre-exposure to sPLA2 completely blocked the aggregating effect of a second dose of sPLA2. Albumin or indomethacin inhibited sPLA2-induced aggregation, similarly to the inhibition of arachidonic acid-induced aggregation. Platelets pre-treated with heparitinase or phosphatidylinositol-specific phospholipase C lost their ability to aggregate in response to sPLA2, although they still responded to other agonists. This suggests that a glycophosphatidylinositol-anchored platelet-membrane heparan sulphate proteoglycan is the binding site for sPLA2 on platelets. Previous reports have stated that sPLA2 is unable to activate platelets. The inhibitory effect of albumin and Mg2+, frequently used in aggregation studies, and the fact that isolated platelets lose their responsiveness to sPLA2 relatively quickly, may explain why the platelet-activating effects of sPLA2 have not been reported earlier.

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Dual Effect of Propranolol on the Human Platelet Activation by Thrombin: Potentiation of Free Intracellular Ca2+ Mobilization and Inhibition of Phospholipase D Activity

Svetlov

Hanahan

1997

Advances in Experimental Medicine and Biology

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The human platelet as a reproducible and sensitive cell for the detection and assay of platelet-activating factor

Cited by 9 publications

References 16 publications

Human platelets respond differentially to lysophosphatidic acids having a highly unsaturated fatty acyl group and alkyl ether-linked lysophosphatidic acids

Human platelets respond differentially to lysophosphatidic acids having a highly unsaturated fatty acyl group and alkyl ether-linked lysophosphatidic acids

Human group II 14 kDa phospholipase A2 activates human platelets

Dual Effect of Propranolol on the Human Platelet Activation by Thrombin: Potentiation of Free Intracellular Ca2+ Mobilization and Inhibition of Phospholipase D Activity

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