Priyadarshini Pantham

Reduced placental amino acid transport in response to maternal nutrient restriction in the baboon

Intrauterine growth restriction increases the risk of perinatal complications and predisposes the infant to diabetes and cardiovascular disease in later life. Mechanisms by which maternal nutrient restriction (MNR) reduces fetal growth are poorly understood. We hypothesized that MNR decreases placental amino acid (AA) transporter activity, leading to reduced transplacental transfer of AAs. Pregnant baboons were fed either a control (ad libitum, n = 7), or MNR diet (70% of control diet, n = 7) from gestational day (GD) 30. At GD 165 (0.9 gestation), placentas (n = 7 in each group) were collected, and microvillous plasma membrane vesicles (MVM) isolated. MVM system A and system L AA transport was determined in vitro using radiolabeled substrates and rapid filtration techniques. In vivo transplacental AA transport was assessed by infusing nine (13)C- or (2)H-labeled essential AA as a bolus into the maternal circulation (n = 5 control, n = 4 MNR) at cesarean section. A fetal vein-to-maternal artery mole percent excess ratio for each essential AA was calculated. Fetal and placental weights were significantly reduced in the MNR group compared with controls (P < 0.01). The activity of system A and system L was markedly reduced by 73 and 84%, respectively, in MVM isolated from baboon placentas at GD 165 following MNR (P < 0.01). In vivo, the fetal vein-to-maternal artery mole percent excess ratio was significantly reduced for leucine, isoleucine, methionine, phenylalanine, threonine, and tryptophan in MNR baboons (P < 0.05). This is the first study to investigate placental AA transport in a nonhuman primate model of MNR. We demonstrate that the downregulation of system A and system L activity in syncytiotrophoblast MVM in MNR leads to decreased transplacental AA transport and, consequently, reduced circulating fetal AA concentrations, a potential mechanism linking maternal undernutrition to reduced fetal growth.

Antiphospholipid antibodies bind syncytiotrophoblast mitochondria and alter the proteome of extruded syncytial nuclear aggregates.

INTRODUCTION Antiphospholipid antibodies (aPL) are autoantibodies that increase the risk of women developing the hypertensive disorder pre-eclampsia. aPL are internalised by the syncytiotrophoblast and increase extrusion of necrotic multinucleated syncytial nuclear aggregates (SNAs), which may trigger endothelial dysfunction in pre-eclampsia. The mechanisms by which aPL alter death processes in the syncytiotrophoblast leading to extrusion of SNAs are unknown. METHODS First trimester human placentae (n = 10) were dissected into explants and cultured either with aPL (50 μg/mL), isotype-matched control antibody (50 μg/mL), or media for 24 h. Harvested SNAs underwent iTRAQ proteomic analysis. Mitochondria in syncytiotrophoblast treated with aPL labelled with FluoroNanogold were visualised using transmission electron microscopy (TEM). RESULTS aPL altered the expression of 72 proteins in SNAs. Thirteen proteins were involved in mitochondrial function. TEM demonstrated that aPL bind to mitochondria in the syncytiotrophoblast and may cause mitochondrial swelling. DISCUSSION aPL disrupt mitochondria increasing the extrusion of SNAs with an altered proteome from the syncytiotrophoblast. These altered SNAs may trigger endothelial dysfunction and pre-eclampsia in these pregnancies.

Transcriptomic analysis of placenta affected by antiphospholipid antibodies: following the TRAIL of trophoblast death

Antiphospholipid antibodies, a maternal risk factor for preeclampsia, increase shedding of necrotic trophoblast debris from the placenta, leading to endothelial dysfunction. Using Affymetrix HGU133 Plus 2 microarrays we found changes in the transcriptome of placental explants treated with antiphospholipid antibodies, including mRNAs BCL2L1, MCL1, PDCD2L, FASLG, SEMA6A, PRKCE and TRAIL that are involved in the regulation of apoptosis. Quantitative real-time RT-PCR and immunohistochemistry confirmed a reduction in TRAIL expression in response to antiphospholipid antibodies. These results may help to understand how antiphospholipid antibodies affect trophoblast cell death and how the antibodies could contribute to the pathogenesis of preeclampsia.

Down-Regulation of Placental Transport of Amino Acids Precedes the Development of Intrauterine Growth Restriction in Maternal Nutrient Restricted Baboons

ABSTRACT Intrauterine growth restriction (IUGR) is an important risk factor for perinatal complications and adult disease. IUGR is associated with down-regulation of placental amino acid transporter expression and activity at birth. It is unknown whether these changes are a cause or a consequence of human IUGR. We hypothesized that placental amino acid transport capacity is reduced prior to onset of reduced fetal growth in baboons with maternal nutrient restriction (MNR). Pregnant baboons were fed either a control (n = 8) or MNR diet (70% of control diet, n = 9) from Gestational Day 30. At Gestational Day 120 (0.65 of gestation), fetuses and placentas were collected. Microvillous (MVM) and basal (BM) plasma membrane vesicles were isolated. System A and system L transport activity was determined in MVM, and leucine transporter activity was assessed in BM using radiolabeled substrates. MVM amino acid transporter isoform expression (SNAT1, SNAT2, and SNAT4 and LAT1 and LAT2) was measured using Western blots. LAT1 and LAT2 expression were also determined in BM. Maternal and fetal plasma amino acids concentrations were determined using mass spectrometry. Fetal and placental weights were unaffected by MNR. MVM system A activity was decreased by 37% in MNR baboon placentas (P = 0.03); however MVM system A amino acid transporter protein expression was unchanged. MVM system L activity and BM leucine transporter activity were not altered by MNR. Fetal plasma concentrations of essential amino acids isoleucine and leucine were reduced, while citrulline increased (P < 0.05) in MNR fetuses compared to controls. In this primate model of IUGR, placental MVM system A amino acid transporter activity is decreased prior to the onset of reduction in the fetal growth trajectory. The reduction in plasma leucine and isoleucine in MNR fetuses may be caused by reduced activity of MVM system A, which is strongly coupled with system L essential amino acid uptake. Our findings indicate that reduced placental amino acid transport may be a cause rather than a consequence of IUGR due to inadequate maternal nutrition.

Antiphospholipid Antibodies Alter Cell-Death-Regulating Lipid Metabolites in First and Third Trimester Human Placentae.

Antiphospholipid antibodies (aPL) are maternal autoantibodies that increase the risk of a woman developing preeclampsia 10‐fold. aPL are internalized into the syncytiotrophoblast and increase extrusion of necrotic trophoblast debris into the maternal blood. This necrotic trophoblast debris may trigger endothelial cell dysfunction contributing to the pathogenesis of preeclampsia. We hypothesize that aPL directly affect placental metabolism, leading to increased syncytiotrophoblast death.