Effects of n-Octyl-β-D-Glucopyranoside on Human and Rat Erythrocyte Membrane Stability against Hemolysis

The practical importance for the pharmaceutical and cosmetics industries of the interactions between biological membranes and surfactant molecules has led to intensive research within this area. The interactions of non-ionic surfactant n-octyl-β-D-glucopyranoside (OG) with the human and rat erythrocyte membranes were studied. The in vitro hemolytic and antihemolytic activities were determined by employing a method in which both erythrocytes were added to the hypotonic medium containing OG at different concentrations, and the amount of haemoglobin released was determined. n-octyl-β-D-glucopyranoside was found to have a biphasic effect on both types of erythrocyte membrane. We also investigated the interactions of OG with the erythrocyte membrane in isotonic medium; the dose-dependent curves show similar behaviour in both human and rat erythrocytes. Our results showed that OG has greater antihemolytic potency on rat than on human erythrocytes; furthermore, rat erythrocytes were more sensitive than human erythrocytes to hypotonic shock. How the different lipoprotein structure of these erythrocytes determines a difference in antihemolytic activity is discussed

Choline modulation of the ABP1-40 channel reconstituited into a model lipid membrane

Nicotinic acetylcholine receptors (AChRs), implicated in memory and learning, in subjects affected by Alzheimer’s disease result altered. Stimulation of α7-nAChRs inhibits amyloid plaques and increases ACh release. β-amyloid peptide (AβP) forms ion channels in the cell and model phospholipid membranes that are retained responsible in Alzheimer disease. We tested if choline, precursor of ACh, could affect the AβP1-40 channels in oxidized cholesterol (OxCh) and in palmitoyl-oleoyl-phosphatidylcholine (POPC):Ch lipid bilayers. Choline concentrations of 5 × 10−11 M–1.5 × 10−8M added to the cis- or trans-side of membrane quickly increased AβP1-40 ion channel frequency (events/min) and ion conductance in OxCh membranes, but not in POPC:Ch membranes. Circular Dichroism (CD) spectroscopy shows that after 24 and 48 hours of incubation with AβP1-40, choline stabilizes the random coil conformation of the peptide, making it less prone to fibrillate. These actions seem to be specific in that ACh is ineffective either in solution or on AβP1-40 channel incorporated into PLMs

AβP1-42 incorporation and channel formation in planar lipid membranes: the role of cholesterol and its oxidation products

Amyloid beta peptide (AP) is a natural peptide, normally released into the cerebrospinal fluid (CSF), that plays a key role in Alzheimer’s disease. The conversion of the peptide from a native soluble form to a non-native and often insoluble form, such as small and large aggregates, protofibrils and fibrils of AP appears to be implicated in the pathogenesis of AD. Although the molecular mechanisms of AP neurotoxicity are not fully understood, a large body of data suggests that the primary target of amyloid peptides is the cell membrane of neurons, that may modulate the structural and functional conversion of AP into assemblies involved in pathological processes. In our study, we provide a systematic investigation of AP1-42’s ability to incorporate and form channel-like events in membranes of different lipid composition and focus on cholesterol and its oxidation products. We propose that cholesterol and its oxidation products can be considered neuroprotective factors because a) by favouring AP1-42 insertion into membranes, the fibrillation/clearance balance shifts toward clearance; b) by shifting channel selectivity toward anions, the membrane potential is moved far from the threshold of membrane excitability, thus decreasing the influx of calcium into the cell

Cholesterol modulates the interaction of some channel-forming peptides

The recent advances in membrane structure and function, describe the membrane as formed by microdomains enriched in cholesterol and glycosphingolipids or lipid rafts implicated in various dynamic cellular processes, such as protein sorting and trafficking, signal transduction processes, modulation of peptide incorporation and channel formation. Cholesterol is present in rapidly changeable pools tightly controlled by a feedback mechanism. The aim of this review is to provide some insight and commentary on how membrane cholesterol modulates the incorporation and channel formation of some peptides. The information gathered in many cases has been transferred to help design new therapeutic substances that improve membrane dysfunction or to biotechnological applications