Modulation of phospholipid asymmetry in synaptosomal membranes by the lipid peroxidation products, 4-hydroxynonenal and acrolein: implications for Alzheimer's disease

Loss of phospholipid asymmetry and elevated brain apoptotic protein levels in subjects with amnestic mild cognitive impairment and Alzheimer disease

“…Mg 2+ ATPase activity-This assay was completed according to previous procedures using FVB mice (Castegna et al, 2004;Sadrzadeh et al, 1993). Synaptosome aliquots (7.5 µg) were suspended in ATPase assay buffer (18 mM histidine, 18 mM imidazole, 80 mM NaCl, 15 mM KCl, 3 mM MgCl 2 , 0.1 mM EGTA, pH 7.1) and treated with 0.1 mM of the Na + K + ATPase inhibitor ouabain to a final volume of 100 µl in a microtiter plate.…”

“…After pretreatment of synaptosomes with NBD-PS, a PtdSer with a fluorescent tag, exposed fluorescence was quenched by chemical modification of the fluorophore employing sodium dithionite (Na 2 S 2 O 4 ), resulting in a decrease in fluorescence for samples compared to control. This method had a value-added characteristic of addressing potential concerns with probe access to the inner leaflet of an unstable system creating incorrect interpretation of asymmetric collapse, as Na 2 S 2 O 4 does not readily diffuse through the plasma membrane (Castegna et al, 2004;Mohmmad Abdul and Butterfield, 2005). Pretreatment with NBD-PS suggested significant exposure of PtdSer in brain from subjects with MCI ( Fig.…”

“…In the event asymmetry is altered, PtdSer is exposed to the cell surface, initiating early stages of apoptosis considered crucial to selective recognition and mononuclear phagocytosis of target cells by macrophages and fibroblasts (Castegna et al, 2004;Fadok et al, 2001;Tyurina et al, 2004b). Exposure of PtdSer to the outer leaflet has been noted to affect protein function involving platelet aggregation, activity of membrane receptors and transport proteins, signal transduction pathways, and cellular morphology via interference with lipidprotein and protein-protein interactions (Balasubramanian and Schroit, 2003;Paulusma and Oude Elferink, 2005;Verkleij and Post, 2000).…”

“…Previous studies have shown that lipid peroxidation, leading to loss of phospholipid asymmetry (Castegna et al, 2004;Kagan et al, 2002;Mohmmad Abdul and Butterfield, 2005), ultimately leads to apoptosis (Fadok et al, 1992;Kagan et al, 2003;Shimohama, 2000). Oxidative stress and oxidative damage, hallmarks of Alzheimer disease (AD) pathology, can lead to increased production of lipid peroxidation products, 4-hydroxynonenal (HNE) and acrolein (2-propenal), in the membrane bilayer (Butterfield et al, 2001;Lovell et al, 2001;Markesbery and Lovell, 1998).…”

“…Oxidative stress and oxidative damage, hallmarks of Alzheimer disease (AD) pathology, can lead to increased production of lipid peroxidation products, 4-hydroxynonenal (HNE) and acrolein (2-propenal), in the membrane bilayer (Butterfield et al, 2001;Lovell et al, 2001;Markesbery and Lovell, 1998). These reactive alkenals have been found to interfere with PtdSer asymmetry via redox dependent flippase (Castegna et al, 2004;Daleke, 2003;Tyurina et al, 2004b). Furthermore, much evidence indicates that oxidative modification of flippase by reactive alkenals and/or apoptotic proteins, resulting in asymmetric collapse (Castegna et al, 2004;Kagan et al, 2002;Mandal et al, 2005;Mohmmad Abdul and Butterfield, 2005;Tyurina et al, 2004a), is greatly elevated in the early apoptotic phenotype of AD models (Herrmann and Devaux, 1990;Kagan et al, 2000).…”