Changes in membrane fluidity and Na⁺/K⁺‐ATPase activity during human trophoblast cell culture

Abstract

The human placenta plays an essential role in embryo development, in particular regulating the transport of ions, nutrients and immunoglobulins from the maternal to the fetal circulation, Trophoblast organization into a syncytial layer involves structural and functional steps that may be monitored and elucidated by in vitro studies. The structural stages by which the syncytial trophoblast is formed are not yet understood. In order to clarify the mechanism of trophoblast development, we studied the morphological characteristics of the syncytial trophoblast formation in culture and the functional changes (transport properties and membrane microviscosity) accompanying the structural modifications.By using both 5-nitroxystearate and 16-nitroxystearate as spin labels, we observed an initial increase in membrane order over 0 -24 h of culture, which can be associated with two events: recovery of cell membranes from trypsin and initial aggregation of cytotrophoblasts. The similar behaviour of the order parameters determined with both probes indicates that membrane order changes both inside and in the outer part of the lipid bilayer. The subsequent decrease in membrane order observed at 36-48 h might be related to the process of cellular fusion.The increase in sodium/potassium pump activity in the first 24 h of culture might be an expression of cell recovery following trypsin treatment. The subsequent decrease might represent an adaptive mechanism by which metabolic energy is mainly used for morphogenetic changes.The human placenta plays an essential role in embryo development, regulating, in particular, the transport of ions, nutrients and immunoglobulins from the maternal to the fetal circulation [ l -51. It also functions as an organ, secreting steroids and hormonal proteins [6].Trophoblast organization into a syncytial layer involves structural and functional steps that may be monitored and elucidated by in vitro studies [7-lo]. The structural stages by which the syncytial trophoblast is formed are not yet fully understood. Some authors believe that the mononucleate cytotrophoblast gives rise to the syncytial trophoblast through a process of differentiation and cellular fusion, while other authors hypothesize that the syncytial trophoblast is organised by means of endomitosis of trophoblast cells [ll -151. In order to clarify the mechanism of this stage of development, we studied the morphological characteristics of syncytial trophoblast formation in culture and the functional

Na+,K+-ATPase of Human Placenta during Gestational Hypertension: A Biochemical—Biophysical Study

“…Such observations support the hypothesis that in GH the same modifications in the transmembrane cation transport as in essential hypertension might occur [4]. The availability of an enzyme model derived from human tissue (i.e.…”

Cardioprotection Induced by Remote Ischemic Preconditioning Preserves the Mitochondrial Respiratory Function in Acute Diabetic Myocardium

“…There is some evidence that RPC might improve respiratory efficiency by preventing uncoupling of oxidative phosphorylation. It has been proposed that the conformation and activity of mitochondrial membrane-bound enzymes such as ATP synthase can be affected by the changes in membrane properties, especially in membrane fluidity (Mazzanti et al 1992, Waczulikova et al 2007. Mitochondrial membrane fluidity is an important biophysical characteristic which refers to the extent of molecular disorder and molecular motion within a lipid bilayer.…”

Neurochemical Evidence that Lysine Inhibits Synaptic Na+,K+-ATPase Activity and Provokes Oxidative Damage in Striatum of Young Rats In vivo

“…Although the mechanisms by which Lys reduced this important activity are presently unknown, changes in membrane fluidity due to membrane lipid oxidation [46][47][48] and/or high vulnerability to free radical attack [49,50] could be responsible for this effect. Changes in membrane fluidity due to Lys are unlikely since they usually occur due to the incorporation of hydrophobic substances into the plasma membrane altering the associations between lipids and the enzyme [47,51,52].…”