Early Stages of Oxidative Stress-Induced Membrane Permeabilization: A Neutron Reflectometry Study

Manuel Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Journal of the American Chemical Society (Impact Factor: 12.11). 04/2009; 131(10):3631-8. DOI: 10.1021/ja807680m
Source: PubMed


Neutron reflectometry was used to probe in situ the structure of supported lipid bilayers at the solid-liquid interface during the early stages of UV-induced oxidative degradation. Single-component supported lipid bilayers composed of gel phase, dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and fluid phase, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), phospholipids were exposed to low-dose oxidative stress generated by UV light and their structures were examined by neutron reflectometry. An interrupted illumination mode, involving exposures in 15 min increments with 2 h intervals between subsequent exposures, and a continuous mode involving a single 60 (or 90) min exposure period were employed. In both cases, pronounced differences in the structure of the lipid bilayer after exposure were observed. Interrupted exposure led to a substantial decrease in membrane coverage but preserved its total thickness at reduced scattering length densities. These results indicate that the initial phase during UV-induced membrane degradation involves the formation of hydrophilic channels within the membrane. This is consistent with the loss of some lipid molecules we observe and attendant reorganization of residual lipids forming hemimicellar edges of the hydrophilic channels. In contrast, continuous illumination produced a graded interface of continuously varied scattering length density (and hence hydrocarbon density) extending 100-150 A into the liquid phase. Exposure of a DPPC bilayer to UV light in the presence of a reservoir of unfused vesicles showed low net membrane disintegration during oxidative stress, presumably because of surface back-filling from the bulk reservoir. Chemical evidence for membrane degradation was obtained by mass spectrometry and Fourier transform infrared spectroscopy. Further evidence for the formation of hydrophilic channels was furnished by fluorescence microscopy and imaging ellipsometry data.

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Available from: Jaroslaw Majewski, Nov 20, 2014
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    • "Degradation of the membrane upon UV exposure causes reorganization of the membrane lipid bilayer that forms hydrophilic and hydrophobic pores within the cellular membrane (Smith et al. 2009). Howland and Parikh (2010) reported that pore formation induced by lipid peroxidation was randomly distributed over the entire membrane surface. "
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    ABSTRACT: The aim of this study was to evaluate the sub-lethal effect of ultraviolet radiation (UV) on the cell growth, intestinal adherence ability and cholesterol removal potential of parent cells and the possible inheritance of such effects on subsequent sub-cultures of Lactobacillus acidophilus BT 1088 cells under conditions that mimic the human gastrointestinal tract. We found that UV decreased (P < 0.05) growth of the parent cells immediately upon treatment (0 h), although an increase (P < 0.05) in growth was observed at 8–24 h of fermentation compared to that of the control. The intestinal adherence ability of the parent cells decreased significantly by 15.62 % (P < 0.05) compared to that of the control. Nevertheless, UV led to increased (>26.22 %; P < 0.05) cholesterol removal from the parent cells, accompanied by an increased incorporation of cholesterol into the cellular membrane and an increased ratio of membrane cholesterol:phospholipids (C:P; P < 0.05; 95 % confidence interval 8.71–121.95 %) in parent cells, compared to that of the control. Incorporated cholesterol was found in the interface of apolar and polar regions, polar heads and also apolar tails of phospholipids in the cellular membrane bilayer. However, such traits were not inherited by the treated cells in subsequent sub-cultures (first, second and third sub-culture). Our data suggest that UV could be a potential physical treatment to increase the cholesterol removal ability of parent cells without inducing permanent damage to the treated cells. UV treatment did not affect the intestinal adherence functionality of the treated cells in subsequent sub-cultures.
    Annals of Microbiology 06/2012; 63(2). DOI:10.1007/s13213-012-0511-y · 0.99 Impact Factor
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    • "By using the same experimental design as in this report, we have found important evidence on Aβ-induced alterations in the lipid content of mitochondrial membranes, in part related possibly to a direct Aβ molecular interaction and in part related to Aβ-induced oxidative stress (unpublished data). Oxidative stress, on the other hand, may induce membrane permeabilization by itself, as revealed by neutron reflectometry in lipid bilayers [63], whereas aging is related to changes in the cholesterol, sphingomyelin, and phospholipid content in membranes [61, 64, 65]. Thus, according to our hypothesis, all these factors are concentrated to facilitate Aβ entry into the cell and eventually to the mitochondria. "
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    ABSTRACT: Amyloid-beta (Aβ) pathology is related to mitochondrial dysfunction accompanied by energy reduction and an elevated production of reactive oxygen species (ROS). Monomers and oligomers of Aβ have been found inside mitochondria where they accumulate in a time-dependent manner as demonstrated in transgenic mice and in Alzheimer's disease (AD) brain. We hypothesize that the internalization of extracellular Aβ aggregates is the major cause of mitochondrial damage and here we report that following the injection of fibrillar Aβ into the hippocampus, there is severe axonal damage which is accompanied by the entrance of Aβ into the cell. Thereafter, Aβ appears in mitochondria where it is linked to alterations in the ionic gradient across the inner mitochondrial membrane. This effect is accompanied by disruption of subcellular structure, oxidative stress, and a significant reduction in both the respiratory control ratio and in the hydrolytic activity of ATPase. Orally administrated melatonin reduced oxidative stress, improved the mitochondrial respiratory control ratio, and ameliorated the energy imbalance.
    Oxidative Medicine and Cellular Longevity 05/2012; 2012(11):843649. DOI:10.1155/2012/843649 · 3.36 Impact Factor
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