Role of placental enzymes and transporters in regulating fetal exposure to pravastatin

University Of Texas Med Br Galveston, Galveston TX

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Abstract

ABSTRACT?Translational Project Currently there are no clinically available agents for the prevention of preeclampsia (PE). The beneficial in vivo and in vitro effects of pravastatin (PRA) in reversing several pathophysiologic pathways associated with PE provided the basis for its use in the prevention of PE. The goal of the proposed investigation is to identify and determine the activity of trophoblast transporters and metabolic enzymes that are involved in the placental biodisposition of PRA and define the extent of fetal exposure to PRA. Recent ex vivo data from our laboratory revealed higher PRA transfer across the placenta than expected from its hydrophilic properties, which suggests the involvement of uptake transporters. Furthermore, transfer of PRA across the dually perfused placental lobule is significantly higher in the Fetal-to-Maternal direction than in the opposite direction, suggesting the involvement of placental efflux transporters. Therefore, it is apparent that the amount of PRA reaching the fetal circulation and, consequently, the extent of fetal exposure to the drug depend on the activity of the uptake and efflux transporters in human placentas. In addition, data from our pilot investigation of PRA pharmacokinetics in pregnant patients revealed that a few patients formed high amounts of its metabolite 3??-isopravastatin (3??-IsoPRA), while others formed low amounts. These data could be explained by patients being fast or slow metabolizers of PRA. Previously, it was suggested that the metabolite is formed by a nonenzymatic, acid-catalyzed transformation of PRA in the stomach, but recent data suggest the involvement of sulfotransferases (SULTs) in the biotransformation of PRA. Since several SULT isoforms are expressed and active in human placentas, it is possible that human placental SULTs are also involved in the metabolism of PRA. Furthermore, the expression and activity of several drug transporters in rat livers were altered by experimentally-induced inflammation. Since pathological changes associated with PE induce an inflammatory cascade, it is possible that PE may also affect the expression and function of placental transporters and metabolic enzymes involved in the biodisposition of PRA. Therefore, we hypothesize that (1) several placental uptake and efflux transporters as well as SULT enzymes are involved in the biodisposition of PRA and consequently affect the extent of fetal exposure and (2) the expression and activities of these transporters and enzymes in the placenta are affected by the pathological changes/ inflammation associated with preeclampsia. Therefore, Specific aim 1 is to identify and determine the activities of the uptake and efflux transporters involved in the biodisposition of PRA in placentas obtained from uncomplicated pregnancies, Specific aim 2 is to identify and determine the activities of SULT enzymes involved in the biotransformation of PRA in placentas obtained from uncomplicated pregnancies, and Specific aim 3 is to determine the effect of preeclampsia on the activities and mRNA and protein expression of placental transporters and enzymes involved in the transfer and biotransformation of PRA, respectively.