Human platelets secrete the plasma type of platelet-activating factor acetylhydrolase primarily associated with microparticles
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Mitsios, J. V.
Vini, M. P.
Stengel, D.
Ninio, E.
Tselepis, A. D.
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peer reviewed
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Arteriosclerosis Thrombosis and Vascular Biology
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Objective-Platelet-activating factor acetylhydrolase (PAF-AH) expresses a Ca2+-independent phospholipase A, activity and hydrolyzes platelet-activating factor as well as oxidized phospholipids. Two major types of PAF-AH have been described: the plasma type, which is associated with lipoproteins, and the intracellular type II PAF-AH. Methods and Results-We investigated the type(s) of PAF-AH expressed in human platelets as well as the mechanism and the enzyme type secreted from platelets during activation. The majority of the enzyme activity (75.1 +/- 14.3% of total) is found in the cytosol, whereas 24.9 +/- 7.3% is associated with the membranes. Immunofluorescence microscopy studies and Western blotting analysis showed that platelets contain the plasma type as well as the intracellular type II PAF-AH. Furthermore, platelets contain high levels of the mRNA of plasma PAF-AH, whereas only a small quantity of the type II PAF-AH mRNA was detected. On activation, platelets secrete the plasma type of PAF-AH mainly associated with platelet-derived microparticles (PMPs). The enzyme activity was also detected on circulating PMPs in plasma from normolipidemic healthy subjects. Conclusion-This is the first indication that in addition to lipoproteins, PAF-AH in human plasma is carried by PMPs, suggesting that the PMP-associated PAF-AH may play a role in the dissemination of biological activities mediated by these particles.
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atherosclerosis, inflammation, paf, paf-acetyhydrolase, pmps, lipoprotein-associated phospholipase-a2, paf-degrading acetylhydrolase, acute coronary syndromes, membrane microparticles, bioactive lipids, shear-stress, procoagulant, enzyme, purification, inhibitor
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<Go to ISI>://000239391400034
http://atvb.ahajournals.org/content/26/8/1907.full.pdf
http://atvb.ahajournals.org/content/26/8/1907.full.pdf
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en
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Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας