Key Points When activated and in platelet storage bags, platelets release respiratory-competent mitochondria, a recognized damage-associated molecular pattern. Mitochondria, descendant of Rickettsia prowazekii, serve as substrate for bactericidal sPLA2-IIA to promote inflammation.

Key Points Activated platelets release microRNA miR-223 preferentially through MPs that can be internalized by endothelial cells. Platelet MP-derived Ago2•microRNA complexes are functional and can regulate endogenous gene expression in recipient endothelial cells.