Clinical review: Circulating microparticles - a new player in sepsis?

In sepsis, inflammation and thrombosis are both the cause and the result of interactions between circulating (e.g. leukocytes and platelets), endothelium and smooth muscle cells. Microparticles are proinflammatory and procoagulant fragments originating from plasma membrane generated after cellular activation and released in body fluids. In the vessel, they constitute a pool of bioactive effectors pulled from diverse cellular origins and may act as inter-cellular messengers. Microparticles expose phosphatidylserine, a procoagulant phospholipid made accessible after membrane remodelling and eventually Tissue Factor, the initiator of blood coagulation at endothelial and leukocyte surface. They constitute a secretion pathway for IL-1beta and up-regulate the proinflammatory response of target cells. Microparticles circulate at low levels in healthy individuals, but undergo phenotypic and quantitative changes eventually playing a pathophysiological role in inflammatory diseases. Microparticles may participate in the pathogenesis of sepsis through multiple ways. They are able of regulating vascular tone and are potent vascular proinflammatory and procoagulant mediators. Microparticle abilities are of increasing interest in the deciphering of the mechanisms that tune multiple organ dysfunction of septic shock.Key words: Microparticles / Bioactive effectors / Sepsis / inflammation / Coagulopathy.