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

CASTRO PARODI M; MARTÍNEZ 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 propertiesare greatly influenced and modulated by the physical state of the membranelipid bilayer and by protein-lipid interactions. The plasma membraneof the syncytiotrophoblast is unusual in comparison to other celltypes. The syncytiotrophoblast is a polarized epithelial layer of multinucleatedsyncytium, with its apical brush border membrane (BBM) facingthe maternal circulation and the smooth basal membrane (BM) facing thefetal circulation. Sphingomyelins (SMs) and phosphatidylcholines (PCs)are major lipid classes in the mammalian cell plasma membrane. In previousexperiments, in normal placenta we found that the amount of SMs ishigher than in other tissues.In addition, accumulated evidence suggests that the expression of a varietyof syncytiotrophoblast transporters is reduced or abnormal in pathologicalplacentas such as preeclamptic placentas. However, the inductor mechanismfor these changes is unknown.Objective: To analyze the lipid composition and biophysical properties ofsyncytiotrophoblast membranes of preeclamptic placentas.Methods: Lipids were extracted by the Bligh-Dyer method and phospholipidsseparated by thin layer chromatography and quantified by Fiske-Subarrow. Cholesterol was determined by a commercial kit. Membranefluidity was evaluated by electron paramagnetic resonance. SM molecularspecies were analyzed and quantified by gas-liquid chromatography andmass spectrometry.Results: In preeclamptic placentas, we observed an increase in SM in theapical membranes of syncytiotrophoblast without changes in cholesterolamount. In addition, membrane fluidity decreased significantly and wealso found an increase in long and unsaturated fatty acids of SM.Conclusions: Our results show that the apical membrane of the syncytiotrophoblastis more rigid in the preeclamptic placentas than in normalones, due to an increase in SM content.We hypothesize that the increase inthe amount of a long and unsaturated SM molecular species disrupts theability of SM to assemble into lipid rafts in the luminal leaflet of the bilayer,creating an unfavorable environment for appropriate location of placentaltransporters in the plasma membrane.