Existence of lipid microdomains in bilayer of dipalmitoyl phosphatidylcholine (DPPC) and 1-stearoyl-2-docosahexenoyl phosphatidylserine (SDPS) and their perturbation by chlorpromazine : A 13C and 31P solid-state NMR study

Effects and Location of Coplanar and Noncoplanar PCB in a Lipid Bilayer: A Solid-State NMR Study

Coplanar and noncoplanar polychlorinated biphenyls (PCBs) are known to have different routes and degree of toxicity. Here, the effects of noncoplanar PCB 52 and coplanar PCB 77 present at 2 mol % in a model system consisting of POPC liposomes (50% hydrated) are investigated by solid-state (13)C and (31)P NMR at 298 K. Both PCBs intercalate horizontally in the outer part of the bilayer, near the segments of the acyl chain close to the glycerol group. Despite similar membrane locations, the coplanar PCB 77 shows little effect on the bilayer properties overall, except for the four nearest neighboring lipids, while the effect of PCB 52 is more dramatic. The first ∼2 layers of lipids around each PCB 52 in the bilayer form a high fluidity lamellar phase, whereas lipids beyond these layers form a lamellar phase with a slight increase in fluidity compared to a bilayer without PCB 52. Further, a third high mobility domain is observed. The explanation for this is the interference of several high fluidity lamellar phases caused by interactions of PCB 52 molecules in different leaflets of the model bilayer. This causes formation of high curvature toroidal region in the bilayer and might induce formation of channels.

A quantum theory for the irreplaceable role of docosahexaenoic acid in neural cell signalling throughout evolution

Six hundred million years ago, the fossil record displays the sudden appearance of intracellular detail and the 32 phyla. The "Cambrian Explosion" marks the onset of dominant aerobic life. Fossil intracellular structures are so similar to extant organisms that they were likely made with similar membrane lipids and proteins, which together provided for organisation and specialisation. While amino acids could be synthesised over 4 billion years ago, only oxidative metabolism allows for the synthesis of highly unsaturated fatty acids, thus producing novel lipid molecular species for specialised cell membranes. Docosahexaenoic acid (DHA) provided the core for the development of the photoreceptor, and conversion of photons into electricity stimulated the evolution of the nervous system and brain. Since then, DHA has been conserved as the principle acyl component of photoreceptor synaptic and neuronal signalling membranes in the cephalopods, fish, amphibian, reptiles, birds, mammals and humans. This extreme conservation in electrical signalling membranes despite great genomic change suggests it was DHA dictating to DNA rather than the generally accepted other way around. We offer a theoretical explanation based on the quantum mechanical properties of DHA for such extreme conservation. The unique molecular structure of DHA allows for quantum transfer and communication of π-electrons, which explains the precise depolarisation of retinal membranes and the cohesive, organised neural signalling which characterises higher intelligence.

Thermal, dynamic and structural properties of drug AT1 antagonist olmesartan in lipid bilayers

It is proposed that AT1 antagonists (ARBs) exert their biological action by inserting into the lipid membrane and then diffuse to the active site of AT1 receptor. Thus, lipid bilayers are expected to be actively involved and play a critical role in drug action. For this reason, the thermal, dynamic and structural effects of olmesartan alone and together with cholesterol were studied using differential scanning calorimetry (DSC), 13C magic-angle spinning (MAS) nuclear magnetic resonance (NMR), cross-polarization (CP) MAS NMR, and Raman spectroscopy as well as small- and wide angle X-ray scattering (SAXS and WAXS) on dipalmitoyl-phosphatidylcholine (DPPC) multilamellar vesicles. 13C CP/MAS spectra provided direct evidence for the incorporation of olmesartan and cholesterol in lipid bilayers. Raman and X-ray data revealed how both molecules modify the bilayer's properties. Olmesartan locates itself at the head-group region and upper segment of the lipid bilayers as 13C CP/MAS spectra show that its presence causes significant chemical shift changes mainly in the A ring of the steroidal part of cholesterol. The influence of olmesartan on DPPC/cholesterol bilayers is less pronounced. Although, olmesartan and cholesterol are residing at the same region of the lipid bilayers, due to their different sizes, display distinct impacts on the bilayer's properties. Cholesterol broadens significantly the main transition, abolishes the pre-transition, and decreases the membrane fluidity above the main transition. Olmesartan is the only so far studied ARB that increases the gauche:trans ratio in the liquid crystalline phase. These significant differences of olmesartan may in part explain its distinct pharmacological profile.

Modification of membrane heterogeneity by antipsychotic drugs: an X-ray diffraction comparative study

Lipid mixtures are used to mimic biological membranes as they allow characterization of lipid lateral domains defined by their specific lipid molecular organization. Therapeutic agents such as antipsychotic drugs (AP) that may interact with lipids arrangement are likely to modify membrane biological properties. The present study describes the effect of 2 typical and 5 atypical antipsychotic drugs on an aqueous co-dispersion of a lipid mixture made of egg phosphatidylcholine (PC)/brain sphingomyelin (SM)/cholesterol (1/1/1 mol/mol/mol). Lamellar liquid-ordered (Lo) and liquid-disordered (Ld) phase coexistence was identified in the control and antipsychotic-added mixtures at 37 degrees C using synchrotron small-angle X-ray scattering methods (XRD). Intensity of the Bragg peaks was used to generate electron density profiles (EDP) allowing bilayer thickness calculation. All antipsychotic except from amisulpride induced a Lo phase bilayer thickness (d(pp)) decrease. Chlorpromazine, haloperidol, amisulpride and 9-0H-risperidone induced a Ld d(pp) increase while ziprazidone, risperidone and clozapine induced a Ld d(pp) decrease, indicating that antipsychotic atypicality is not associated with a specific d(pp) modification on our lipid model mixture. Results are discussed in terms of competition of antipsychotic compounds with cholesterol and mode of reorganization of lateral domains. A pharmacological relevance of these changes is also discussed.

Olanzapine interaction with dipalmitoyl phosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoyl phosphatidylserine (POPS) bilayer: a (13)C and (31)P solid-state NMR study

Phospholipid bilayer interaction of olanzapine (OLZ), a thienobenzodiazepine derivative and an antipsychotic agent, has been studied with (13)C and (31)P solid-state NMR. A dipalmitoyl phosphatidylcholine (60%)/1-palmitoyl-2-oleoyl phosphatidylserine (40%) bilayer (DPPC(60%)/POPS(40%)) with 50 wt.% H(2)O, with and without 10 mol% OLZ have been investigated. The results reveal that both the serine and the choline head groups are affected by OLZ interaction with the bilayer. The OLZ interaction with the serine and the choline head groups appears to be caused by electrostatic attraction to the serine head group carboxyl and repulsion of the choline head group positively charged nitrogen. (31)P MAS NMR experiments show the appearance of two new (31)P resonances both for the PS and the PC phosphorous in the presence of OLZ. Static (31)P NMR spectra demonstrate a decrease in chemical shift anisotropy (CSA) of the OLZ containing bilayer when in the liquid-crystalline phase and an increase in CSA when in the gel state.

The psychotropic drug olanzapine (Zyprexa) increases the area of acid glycerophospholipid monolayers

The typical antipsychotics chlorpromazine (CPZ) and trifluoperazine (TFP) increase the mean molecular area (mma) of acidic, but not neutral, glycerophospholipids in monolayers at pH 7.36 measured by the Langmuir technique. The atypical antipsychotic olanzapine (OLP(1)) is structurally similar to TFP. We have therefore studied the effects of OLP on glycerophospholipid monolayers and in comparison with CPZ. Olanzapine (10 microM, in subphase, pH 7.36) influenced the isotherms (surface pressure versus mma) in monolayers of the neutral dipalmitoyl phosphatidylcholine (DPPC) and the acidic dipalmitoyl phosphatidylserine (DPPS) or 1-palmitoyl-2-oleoylphosphatidylserine (POPS) in the increasing order of mma: DPPS<DPPC<POPS at both lower and higher temperature. Thus, presence of an unsaturated acyl in PS increased the drug-induced effect on mma. The mma in the absence of drugs was lower at lower temperatures than at higher temperatures. OLP affected mma to a greater extent than CPZ, and caused the greatest interaction at surface pressure of 30 mN/m at higher temperatures. In contrast, CPZ gave the largest effect in the monolayers at surface pressure 30 mN/m at lower temperatures. CPZ did not alter the isotherms of DPPC, at lower or higher temperature, and only affected the packing of the DPPS and POPS monolayers. In contrast, OLP altered the isotherms of DPPC. It is suggested that the drugs affect the monolayer packing by intercalating between the glycerophospholipid molecules. Since CPZ has major side effects, while OLP has few, this may indicate that there is poor correlation between side effects and effects of the drugs on phospholipid monolayers.

Thermodynamic and Infrared Analyses of the Interaction of Chlorpromazine with Phospholipid Monolayers

An investigation has been made of the interaction between chlorpromazine (CPZ) and monolayers of 1,2-dipalmitoyl-sn-3-glycerophosphatidylcholine (DPPC) and 1,2-dipalmitoyl-sn-3-glycero[phospho-rac-(1-glycerol)] (DPPG), both at the air/water interface and in transferred Langmuir-Blodgett films. The Gibbs free energy, DeltaG, and the compressibility modulus (C(S)(-1)), obtained from the surface pressure isotherms, indicated changes in the in-plane interactions of CPZ/DPPG mixed monolayers, with positive values of DeltaG. The arrangement of CPZ in the zwitterionic DPPC monolayers causes a weaker interaction in CPZ/DPPC mixed monolayers, with the DeltaG fluctuating around zero. IR measurements in transferred monolayers showed that CPZ did not affect the conformational order of the acyl chains, its effects being limited to the bands corresponding to the headgroups. Furthermore, since no shift was observed for the acyl chain bands, the phase transition induced by CPZ is not a liquid expanded (LE) to liquid condensed (LC) transition, as the latter is associated with chain ordering. Taken together, the IR and compressibility results demonstrate that the effect from CPZ cannot be correlated with temperature changes in the subphase for pure monolayers, in contrast to models proposed by other authors.