OBJECTIVE: Platelet-activating factor acetylhydrolase (PAF-AH) expresses a Ca2+-independent phospholipase A2 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. CONCLUSIONS: 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.
OBJECTIVE:Platelet-activating factor acetylhydrolase (PAF-AH) expresses a Ca2+-independent phospholipase A2 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. CONCLUSIONS: 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.
Authors: Alexandros D Tselepis; George Hahalis; Constantinos C Tellis; Eleni C Papavasiliou; Panagiota T Mylona; Alexandra Kourakli; Dimitrios C Alexopoulos Journal: J Lipid Res Date: 2010-07-12 Impact factor: 5.922
Authors: Lawrence L Horstman; Wenche Jy; Yeon S Ahn; Robert Zivadinov; Amir H Maghzi; Masoud Etemadifar; J Steven Alexander; Alireza Minagar Journal: J Neuroinflammation Date: 2010-02-03 Impact factor: 8.322
Authors: Jason M Foulks; Gopal K Marathe; Noemi Michetti; Diana M Stafforini; Guy A Zimmerman; Thomas M McIntyre; Andrew S Weyrich Journal: Blood Date: 2009-04-24 Impact factor: 22.113
Authors: Ines Galtier d'Auriac; Robert A Quinn; Heather Maughan; Louis-Felix Nothias; Mark Little; Clifford A Kapono; Ana Cobian; Brandon T Reyes; Kevin Green; Steven D Quistad; Matthieu Leray; Jennifer E Smith; Pieter C Dorrestein; Forest Rohwer; Dimitri D Deheyn; Aaron C Hartmann Journal: Proc Biol Sci Date: 2018-08-15 Impact factor: 5.349