LIPID COMPOSITION AND BIOPHYSICAL PROPERTIES OF APICAL AND BASAL MEMBRANES OF PREECLAMPTIC PLACENTAS

CASTRO PARODI M; MARTINEZ N; MATE S; HERLAX V; FARINA M ; DAMIANO A

Simposio; VI LatinAmerican Symposium on Maternal-Fetal Interaction & Placenta; 2015

Transport activities together with other membrane-associated properties are greatly influenced and modulated by the physical state of the membrane lipid bilayer and by protein-lipid interactions. The plasma membrane of the syncytiotrophoblast is unusual in comparison to other cell types. The syncytiotrophoblast is a polarized epithelial layer of multinucleated syncytium, with its apical brush border membrane (BBM) facing the maternal circulation and the smooth basal membrane (BM) facing the fetal circulation. Sphingomyelins (SMs) and phosphatidylcholines (PCs) are major lipid classes in the mammalian cell plasma membrane. In previous experiments, in normal placenta we found that the amount of SMs is higher than in other tissues. In addition, accumulated evidence suggests that the expression of a variety of syncytiotrophoblast transporters is reduced or abnormal in pathological placentas such as preeclamptic placentas. However, the inductor mechanism for these changes is unknown. Objective: To analyze the lipid composition and biophysical properties of syncytiotrophoblast membranes of preeclamptic placentas. Methods: Lipids were extracted by the Bligh-Dyer method and phospholipids separated by thin layer chromatography and quantified by Fiske- Subarrow. Cholesterol was determined by a commercial kit. Membrane fluidity was evaluated by electron paramagnetic resonance. SM molecular species were analyzed and quantified by gas-liquid chromatography and mass spectrometry. Results: In preeclamptic placentas, we observed an increase in SM in the apical membranes of syncytiotrophoblast without changes in cholesterol amount. In addition, membrane fluidity decreased significantly and we also found an increase in long and unsaturated fatty acids of SM. Conclusions: Our results show that the apical membrane of the syncytiotrophoblast is more rigid in the preeclamptic placentas than in normal ones, due to an increase in SM content.We hypothesize that the increase in the amount of a long and unsaturated SM molecular species disrupts the ability of SM to assemble into lipid rafts in the luminal leaflet of the bilayer, creating an unfavorable environment for appropriate location of placental transporters in the plasma membrane.