Human plasma platelet‐derived exosomes: effects of aspirin

Platelet‐derived exosomes mediate platelet atherogenic interactions with endothelial cells and monocytes. A new method for isolation of plasma platelet‐derived exosomes is described and used to examine effects of aging and aspirin on exosome cargo proteins. Exosome secretion by purified platelets in vitro did not increase after exposure to thrombin or collagen, as assessed by exosome counts and quantification of the CD81 exosome marker. Thrombin and collagen increased exosome content of α‐granule chemokines CXCL4 and CXCL7 and cytoplasmic high‐mobility group box 1 (HMGB1) protein, but not membrane platelet glycoprotein VI (GPVI), with dependence on extracellular calcium. Aspirin consumption significantly blocked thrombin‐ and collagen‐induced increases in exosome cargo levels of chemokines and HMGB1, without altering total exosome secretion or GPVI cargo. Plasma platelet‐derived exosomes, enriched by absorption with mouse antihuman CD42b [platelet glycoprotein Ib (GPIb)] mAb, had sizes and cargo protein contents similar to those of exosomes from purified platelets. The plasma platelet‐derived exosome number is lower and its chemokine and HMGB1 levels higher after age 65 yr. Aspirin consumption significantly suppressed cargo protein levels of plasma platelet‐derived exosomes without altering total levels of exosomes. Cargo proteins of human plasma platelet‐derived exosomes may biomark platelet abnormalities and in vivo effects of drugs.—Goetzl, E. J., Goetzl, L., Karliner, J. S., Tang, N., Pulliam, L. Human plasma platelet‐derived exosomes: effects of aspirin. FASEB J. 30, 2058–2063 (2016). www.fasebj.org