Cholesterol attenuates and prevents bilayer damage and breakdown in lipoperoxidized model membranes. A spin labeling EPR study

Abstract

The stabilizing effect of cholesterol on oxidized membranes has been studied in planar phospholipid bilayers and multilamellar 1-palmitoyl-2-linoleoyl-phosphatidylcholine vesicles also containing either 1-palmitoyl-2glutaroyl-phosphatidylcholine or 1-palmitoyl-2-(13-hydroxy-9,11-octadecanedienoyl)-phosphatidylcholine oxidized phosphatidylcholine in variable ratio. Lipid peroxidation-dependent membrane alterations in the absence and in the presence of cholesterol were analyzed using Electron Paramagnetic Resonance spectroscopy of the model membranes spin labelled with either cholestane spin label (3-DC) or phosphatidylcholine spin label (5-DSPC). Cholesterol, added to lipid mixtures up to 40% final molar ratio, decreased the inner bilayer disorder as compared to cholesterol-free membranes and strongly reduced bilayer alterations brought about by the two oxidized phosphatidylcholine species. Furthermore, Sepharose 4B gel-chromatography and cryo electron microscopy of aqueous suspensions of the lipid mixtures clearly showed that cholesterol is able to counteract the micelle forming tendency of pure 1-palmitoyl-2-glutaroyl-phosphatidylcholine and to sustain multilamellar vesicles formation. It is concluded that membrane cholesterol may exert a beneficial and protective role against bilayer damage caused by oxidized phospholipids formation following reactive oxygen species attack to biomembranes.

Protective effect of cholesterol-loaded cyclodextrin pretreatment against hydrogen peroxide induced oxidative damage in ram sperm

“…Based upon the present findings it can be elucidated that cholesterol incorporation in sperm membrane attenuated the oxidative damage either through stabilizing the membrane or maintaining the antioxidant enzyme defence system. This assumption confirms the previous reports that increased membrane cholesterol contents has a stabilizing role in oxidised membrane [18,23]. In future studies, there is need to explore the spontaneous lipid peroxidation and antioxidant enzyme level in CLC treated sperm after freezing and thawing.…”

“…During the last decade many studies have been conducted to elucidate the protective effect of CLC during cryopreservation. Moreover, it has been stated that cholesterol directly modulates the physical properties of lipid bilayer and alter the membrane response to the degenerative processes including lipid peroxidation in different biological systems [31,23,25]. Until now enhanced osmotic tolerance, membrane fluidity and reduced cryocapacitation/premature acrosome reaction are the outcomes of CLC which are considered/proposed as possible reasons behind improved cryosurvival rate of CLC treated sperm [2,3,12,24,36,45].…”

Molecular-Scale Biophysical Modulation of an Endothelial Membrane by Oxidized Phospholipids

“…Indeed, previous computational studies show that cholesterol addition to bilayers containing PGPC causes reduced mobility of PGPC (77), decreased bilayer lipid disorder (81), and reversed disordering effects of PGPC. One proposed explanation is that cholesterol fills the voids left by the reoriented truncated tails (76).…”

Does hydrogen bonding contribute to lipoperoxidation-dependent membrane fluidity variation? An EPR-spin labeling study

“…[16]. According to its definition, R″-value increases with the degree of bilayer disorder, while B/C parameter decreases [17]. In some instances, the order parameter S value was estimated from SPB parallel/ perpendicular EPR spectral pairs according to Ref [18].…”

“…The packing order of the hydrophobic core of diHpLPC-containing membranes was investigated by EPR spectroscopy of Supported Phospholipid Bilayers (SPB) spin labelled with different lipid spin probes, as previously described [17]. The bilayer structure of SPB, even in case of heavy oxidation, is guaranteed by the membrane forming ability of diHpLPC previously demonstrated by gel-chromatography and DLS, so that the loss of EPR spectral anisotropy in SPB can be attributed to misaligning of fatty acid chains rather than to scrambling of the bilayer structure, as previously stated [4,8,[15][16][17], also in keeping with other studies [25][26][27].…”