Platelet microparticles: a carrier of platelet-activating factor?

Area of Science:

• Hematology
• Biochemistry
• Cell Biology

Background:

• Platelet-activating factor (PAF) is traditionally considered a soluble mediator released from activated platelets.
• Platelet activation also results in the release of numerous microparticles.
• The precise localization and release mechanism of PAF from activated platelets remain incompletely understood.

Purpose of the Study:

• To investigate whether microparticles released from activated platelets contain Platelet-activating factor (PAF).
• To quantify the amount of PAF associated with whole platelets, microparticles, and the suspending medium after activation.
• To explore the susceptibility of microparticle-associated PAF to plasma enzymes.

Main Methods:

• Platelets were activated using a combination of thrombin and collagen.
• PAF levels were quantified in whole activated platelets, released microparticles, and the supernatant using a bioassay.
• The susceptibility of released PAF to plasma acetylhydrolase was assessed.

Main Results:

• A significant amount of PAF (4.6 +/- 1.5 x 10(-12) mol from 3 x 10(8) platelets) was released upon activation.
• Eighty-seven percent of the released PAF was found to be associated with microparticles.
• PAF localized on microparticles demonstrated susceptibility to plasma acetylhydrolase.

Conclusions:

• Microparticles serve as a primary carrier for Platelet-activating factor (PAF) released from activated platelets.
• This finding challenges the traditional view of PAF as solely a soluble mediator.
• Microparticle-associated PAF represents a potentially important, cell-derived mediator with implications for localized biological responses.