Lipoproteins and prostacyclin stability.

PGI2 is an important local mediator keeping circulating blood cells apart from the vessel wall, thus regulating hemostasis. Alterations of locally available amounts of this compound may be associated with either bleeding or thrombotic events. Factors influencing synthesis, transmission, and degradation coregulate the amount of biologically active PGI2 available at a certain vascular site. Plasmatic T1/2 of PGI2 is shortened either due to an inherited disorder or an acquired disease, its underlying cause being unknown. Generally, this is associated with thrombotic events and extremely low concentrations of both HDL cholesterol and apoA1. In contrast, the only patient we saw with a prolonged PGI2 T1/2 repeatedly experienced extremely severe bleeding complications. Recovery from severe diseases such as shock and malaria, for example, results in normalization of both PGI2 T1/2 and lipoprotein (HDL) and apoA values. Although these findings have not yet been verified at a molecular level, it is likely, that apoA1 contributes to the stabilization of PGI2 in human blood, thus representing one further link between lipid metabolism and hemostasis.