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Excessive expression of subunit 1 of GIRK1 in ER+ breast tumors is associated with reduced survival times and increased lymph node metastasis in patients. To investigate possible tumor-initiating properties, benign MCF10A and malign MCF7 mammary epithelial cells were engineered to overexpress GIRK1 neoplasia associated vital parameters and resting potentials were measured and compared to controls. The presence of GIRK1 resulted in resting potentials negative to the controls. Upon GIRK1 overexpression, several cellular pathways were regulated towards pro-tumorigenic action as revealed by comparison of transcriptomes of MCF10AGIRK1 with the control (MCF10AeGFP). According to transcriptome analysis, cellular migration was promoted while wound healing and extracellular matrix interactions were impaired. Vital parameters in MCF7 cells were affected akin the benign MCF10A lines, but to a lesser extent. Thus, GIRK1 regulated cellular pathways in mammary epithelial cells are likely to contribute to the development and progression of breast cancer.

Background Endogenously expressed microRNAs (miRNAs) have attracted attention as important regulators in post-transcriptionally controlling gene expression of various physiological processes. As miRNA dysregulation is often associated with various disease patterns, such as obesity, miRNA-27a might therefore be a promising candidate for miRNA mimic replacement therapy by inhibiting adipogenic marker genes. However, application of naked nucleic acids faces some limitations concerning poor enzymatic stability, bio-membrane permeation and cellular uptake. To overcome these obstacles, the development of appropriate drug delivery systems (DDS) for miRNAs is of paramount importance. Methods In this work, a triple combination of atomic force microscopy (AFM), brightfield (BF) and fluorescence microscopy was used to trace the cellular adhesion of N-TER peptide-nucleic acid complexes followed by time-dependent uptake studies using confocal laser scanning microscopy (cLSM). To reveal the biological effect of miRNA-27a on adipocyte development after transfection treatment, Oil-Red-O (ORO)- staining was performed to estimate the degree of in lipid droplets accumulated ORO in mature adipocytes by using light microscopy images as well as absorbance measurements. Results The present findings demonstrated that amphipathic N-TER peptides represent a suitable DDS for miRNAs by promoting non-covalent complexation through electrostatic interactions between both components as well as cellular adhesion of the N-TER peptide - nucleic acid complexes followed by uptake across cell membranes and intracellular release of miRNAs. The anti-adipogenic effect of miRNA-27a in 3T3-L1 cells could be detected in mature adipocytes by reduced lipid droplet formation. Conclusion The present DDS assembled from amphipathic N-TER peptides and miRNAs is capable of inducing the anti-adipogenic effect of miRNA-27a by reducing lipid droplet accumulation in mature adipocytes. With respect to miRNA mimic replacement therapies, this approach might provide new therapeutic strategies to prevent or treat obesity and obesity-related disorders.

Objectives The design of nanocarriers for local drug administration to the lining mucosa requires a sound knowledge of how nanoparticles (NPs) interact with saliva. This contact determines whether NPs agglomerate and become immobile due to size- and interaction-filtering effects or adsorb on the cell surface and are internalized by epithelial cells. The aim of this study was to examine the behavior of NPs in saliva considering physicochemical NP properties. Materials and methods The salivary pore–size distribution was determined, and the viscosity of the fluid inside of the pores was studied with optical tweezers. Distinct functionalized NPs (20 and 200 nm) were dispersed in saliva and salivary buffers and characterized, and surface-bound MUC5B and MUC7 were analyzed by 1D electrophoresis and immunoblotting. NP mobility was recorded, and cellular uptake studies were performed with TR146 cells. Results The mode diameter of the salivary mesh pores is 0.7 μm with a peak width of 1.9 μm, and pores are filled with a low-viscosity fluid. The physicochemical properties of the NPs affected the colloidal stability and mobility: compared with non-functionalized particles, which did not agglomerate and showed a cellular uptake rate of 2.8%, functionalized particles were immobilized, which was correlated with agglomeration and increased binding to mucins. Conclusion The present study showed that the salivary microstructure facilitates NP adsorption. However, NP size and surface functionalization determine the colloidal stability and cellular interactions. Clinical relevance The sound knowledge of NP interactions with saliva enables the improvement of current treatment strategies for inflammatory oral diseases. Electronic supplementary material The online version of this article (doi:10.1007/s00784-017-2172-5) contains supplementary material, which is available to authorized users.

Atherosclerosis is a major cardiovascular disease worldwide, that could benefit from innovative nanomedicine imaging tools and treatments. In this perspective, we here studied, by fluorescence imaging in ApoE-/- mice, the biodistribution of non-functionalized and RXP470.1-targeted nanostructured lipid carriers (NLC) loaded with DiD dye. RXP470.1 specifically binds to MMP12, a metalloprotease that is over-expressed by macrophages residing in atherosclerotic plaques. Physico-chemical characterizations showed that RXP-NLC (about 105 RXP470.1 moieties/particle) displayed similar features as non-functionalized NLC in terms of particle diameter (about 60-65 nm), surface charge (about &minus, 5 &mdash, &minus, 10 mV), and colloidal stability. In vitro inhibition assays demonstrated that RXP-NLC conserved a selectivity and affinity profile, which favored MMP-12. In vivo data indicated that NLC and RXP-NLC presented prolonged blood circulation and accumulation in atherosclerotic lesions in a few hours. Twenty-four hours after injection, particle uptake in atherosclerotic plaques of the brachiocephalic artery was similar for both nanoparticles, as assessed by ex vivo imaging. This suggests that the RXP470.1 coating did not significantly induce an active targeting of the nanoparticles within the plaques. Overall, NLCs appeared to be very promising nanovectors to efficiently and specifically deliver imaging agents or drugs in atherosclerotic lesions, opening avenues for new nanomedicine strategies for cardiovascular diseases.

International audience; The objective of our work was to investigate the effects of different types of nanoparticles on endothelial (HUVEC) and monocytic cell functions. We prepared and tested 14 different nanosystems comprising liposomes, lipid nanoparticles, polymer, and iron oxide nanoparticles. Some of the tested nanosystems contained targeting, therapeutic, or contrast agent(s). The effect of particles (0-400 mu g/mL) on endothelial-monocytic cell interactions in response to TNF-alpha was investigated using an arterial bifurcation model and dynamic monocyte adhesion assay. Spontaneous HUVEC migration (0-100 mu g/mL nanoparticles) and chemotaxis of monocytic cells towards MCP-1 in presence of particles (0-400 mu g/mL) were determined using a barrier assay and a modified Boyden chamber assay, respectively. Lipid nanoparticles dose-dependently reduced monocytic cell chemotaxis and adhesion to activated HUVECs. Liposomal nanoparticles had little effect on cell migration, but one formulation induced monocytic cell recruitment by HUVECs under non-uniform shear stress by about 50%. Fucoidan-coated polymer nanoparticles (25-50 mu g/mL) inhibited HUVEC migration and monocytic cell chemotaxis, and had a suppressive effect on monocytic cell recruitment under non-uniform shear stress. No significant effects of iron oxide nanoparticles on monocytic cell recruitment were observed except lauric acid and human albumin-coated particles which increased endothelial-monocytic interactions by 60-70%. Some of the iron oxide nanoparticles inhibited HUVEC migration and monocytic cell chemotaxis. These nanoparticle-induced effects are of importance for vascular cell biology and function and must be considered before the potential clinical use of some of the analyzed nanosystems in cardiovascular applications.

Low-density lipoproteins (LDL) are natural lipid transporter in human plasma whose chemically modified forms contribute to the progression of atherosclerosis and cardiovascular diseases accounting for a vast majority of deaths in westernized civilizations. For the development of new treatment strategies, it is important to have a detailed picture of LDL nanoparticles on a molecular basis. Through the combination of X-ray and neutron small-angle scattering (SAS) techniques with high hydrostatic pressure (HHP) this study describes structural features of normolipidemic, triglyceride-rich and oxidized forms of LDL. Due to the different scattering contrasts for X-rays and neutrons, information on the effects of HHP on the internal structure determined by lipid rearrangements and changes in particle shape becomes accessible. Independent pressure and temperature variations provoke a phase transition in the lipid core domain. With increasing pressure an interrelated anisotropic deformation and flattening of the particle are induced. All LDL nanoparticles maintain their structural integrity even at 3000 bar and show a reversible response toward pressure variations. The present work depicts the complementarity of pressure and temperature as independent thermodynamic parameters and introduces HHP as a tool to study molecular assembling and interaction processes in distinct lipoprotein particles in a nondestructive manner. (Less)

Lipid composition of human low-density lipoprotein (LDL) and its physicochemical characteristics are relevant for proper functioning of lipid transport in the blood circulation. To explore dynamical and structural features of LDL particles with either a normal or a triglyceride-rich lipid composition we combined coherent and incoherent neutron scattering methods. The investigations were carried out under high hydrostatic pressure (HHP), which is a versatile tool to study the physicochemical behavior of biomolecules in solution at a molecular level. Within both neutron techniques we applied HHP to probe the shape and degree of freedom of the possible motions (within the time windows of 15 and 100 ps) and consequently the flexibility of LDL particles. We found that HHP does not change the types of motion in LDL, but influences the portion of motions participating. Contrary to our assumption that lipoprotein particles, like membranes, are highly sensitive to pressure we determined that LDL copes surprisingly well with high pressure conditions, although the lipid composition, particularly the triglyceride content of the particles, impacts the molecular dynamics and shape arrangement of LDL under pressure.

Biological membranes can be targets for compounds that either disrupt their barrier function or affect protein function via membrane-mediated processes. Biophysical studies on membrane-mimetic systems composed of membrane lipids have contributed substantially to our knowledge on the pertaining membrane physics and aid the development of membrane-specific drugs. Moreover, lipid membranes and, in particular, liposomes are convenient systems for drug delivery. We review some of our recent work that demonstrates the applicability of X-ray scattering to understanding the molecular mechanisms of drug-membrane interactions. In particular we focus on effects of anesthetics, sphingomyelinase, and antimicrobial peptides. We further discuss X-ray scattering as a quality-control tool for liposomal drug-delivery systems.

Daniela Frascione,1 Clemens Diwoky,2 Gunter Almer,1,3 Peter Opriessnig,2 Caroline Vonach,1 Kerstin Gradauer,1 Gerd Leitinger,4 Harald Mangge,3 Rudolf Stollberger,2 Ruth Prassl1,51Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, Graz, Austria; 2Institute of Medical Engineering, University of Technology, Graz, Austria; 3Clinical Institute for Medical and Chemical Laboratory Diagnosis (CIMCL), Medical University, Graz, Austria; 4Institute of Cell Biology, Histology and Embryology, Medical University, Graz, Austria; 5Ludwig Boltzmann Institute for Lung Vascular Research, Graz, AustriaBackground: Magnetic liposomes (MLs) are phospholipid vesicles that encapsulate magnetic and/or paramagnetic nanoparticles. They are applied as contrast agents for magnetic resonance imaging (MRI). MLs have an advantage over free magnetic nanocores, in that various functional groups can be attached to the surface of liposomes for ligand-specific targeting. We have synthesized PEG-coated sterically-stabilized magnetic liposomes (sMLs) containing ultrasmall superparamagnetic iron oxides (USPIOs) with the aim of generating stable liposomal carriers equipped with a high payload of USPIOs for enhanced MRI contrast.Methods: Regarding iron oxide nanoparticles, we have applied two different commercially available surface-coated USPIOs; sMLs synthesized and loaded with USPIOs were compared in terms of magnetization and colloidal stability. The average diameter size, morphology, phospholipid membrane fluidity, and the iron content of the sMLs were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence polarization, and absorption spectroscopy, respectively. A colorimetric assay using potassium thiocyanate (KSCN) was performed to evaluate the encapsulation efficiency (EE%) to express the amount of iron enclosed into a liposome. Subsequently, MRI measurements were carried out in vitro in agarose gel phantoms to evaluate the signal enhancement on T1- and T2-weighted sequences of sMLs. To monitor the biodistribution and the clearance of the particles over time in vivo, sMLs were injected in wild type mice.Results: DLS revealed a mean particle diameter of sMLs in the range between 100 and 200 nm, as confirmed by TEM. An effective iron oxide loading was achieved just for one type of USPIO, with an EE% between 74% and 92%, depending on the initial Fe concentration (being higher for lower amounts of Fe). MRI measurements demonstrated the applicability of these nanostructures as MRI probes.Conclusion: Our results show that the development of sMLs is strictly dependent on the physicochemical characteristics of the nanocores. Once established, sMLs can be further modified to enable noninvasive targeted molecular imaging.Keywords: magnetic liposomes, fluorescence polarization, biodistribution, MRI contrast agent&nbsp

Low-density lipoprotein (LDL) is the principal cholesterol transporter in the human blood circulation. The quasi-spherical LDL particles (∼20 nm) are made up of a complex combination of various lipids and a large single amphipathic protein moiety, named apolipoprotein B-100. LDL has a hydrophobic core and an amphiphilic shell. Each particle has a specific phase transition temperature (Tm) corresponding to the melting of the core lipids from an ordered liquid crystalline to a disordered fluid phase.The structural impact of high hydrostatic pressure (HHP) was studied with different types of LDL (native, oxidized and triglyceride rich) with SANS (PSI, Switzerland) and SAXS (Elettra, Italy). The HHP ranged from 50 to 3000 bar. Temperature points were chosen below, on and above Tm.The pair distance distribution functions p(r) of the SAS curves revealed pressure dependent changes of the particle structure seen in the low q-region (∼0.25 nm−1), also reflected by a decrease of Radii of Gyration (Rg) with increasing pressure.Especially the p(r) functions from the SAXS data do not only show an overall particle change but also a highly pressure sensitive inner organization. A triple-peak feature indicating the lamellar lipid organization below Tm was induced by raising the pressure up to 3000 bar. These pressure sensitive lipid layers were observed by scattering intensity changes in SAXS curves at q=1.7 nm−1.The shape alterations could be evidenced by fitting an ellipsoidal model to the SANS curves resulting in a decrease of the ellipsoidal radii under pressure. A new LDL model considering the cross-sectional electron density profile is developed and applied to the SAS data to get a more detailed insight into pressure dependent behavior.

The potential role of human low density lipoprotein (LDL) particles as delivery system for lipophilic, cytotoxic drugs critically depends on their structural integrity. In the present study, LDL particles were loaded with antineoplastic prodrugs, i.e. monooleoyl (MOT)- and dioleoyl (DOT)- thymidine esters by different techniques. Using the reconstitution method MOT shows the highest incorporation efficiency with over 80% of the initial drug associated with LDL. In contrast, for the more lipophilic DOT the incorporation efficiency for reconstitution, dry film as well as dimethylsulfoxide method was extremely low. Structural changes upon drug loading were monitored by differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS). The results show that the influence of MOT and DOT is predominantly confined to the surface monolayer of LDL seen as a destabilisation of the protein moiety and a small increase in particle diameter. The core lipid region of the LDL-drug complexes remains essentially unaffected, as verified by undisturbed core lipid arrangement and core lipid melting behaviour.

This special issue of the European Biophysics Journal marks the contributions of Peter Laggner to molecular biophysics and X-ray and neutron scattering techniques on the occasion of his 68th birthday. Actually, Peter Laggner is not a person who likes to dwell in the past, or talk of the good old days. ‘‘Why look back, if one can look forward?’’, is one of his most popular quotes. Well, we hope that he will forgive us on this one occasion. So, let us look back and recall some of the past from a rich life with many things to remember, but, to make it bearable, we will use an element of humor. Born in Piberbach, Upper Austria, Peter went to Graz to study chemistry and physics. During his PhD, he started with his so successful combination of small-angle X-ray scattering (SAXS), which he learned from the Austrian pioneer in SAXS, Otto Krakty, and biophysics, taught to him by Anton Holasek, then head of the Medical Biochemistry Institute, University of Graz. For his thesis on ‘‘Structure of Antigen Antibody Complexes in Solution by SAXS’’ Peter had an urgent need for blood. Therefore, this part of his career truly was bloody. Using his own car he would go to the slaughterhouse to fetch swine blood in buckets and then drive back to his laboratory. Occasionally blood spilled over. Who cares? In the laboratory the tedious job of precipitation and centrifugation awaited him, accompanied by anxious moments when the rotor lifted and the centrifuge started to move around. By dawn his eyes were blood-shot, but the proteins were prepared and ‘‘real science’’ could start. Soon afterwards lipoproteins—high-density (HDL) and low-density lipoproteins (LDL)—caught Peter’s scientific interest. Again, blood had to be isolated, and trouble started from the beginning. This time the blood had to be of human origin. Thus, healthy normolipidemic volunteers were required. By chance, PhD students were ‘‘lucky’’ to act as donors for Peter’s blood pool, but the most fascinating thing was, however, to use one’s own blood, as he always told us. Later, lipoprotein subspecies came in from John Chapman in Paris, making life much easier. However, whenever whole blood was harvested in our laboratory, Peter was among the first to put his name on the list of donors, eager to support our common efforts to solve the structure of LDL. One day, early in the morning, Peter arrived at the laboratory with a bottle of warm blood in his hands and laughed, ‘‘Hey girls, I have been at the doctor and thought I could bring you some fresh blood!’’, remembers Ruth Prassl. Peter’s pioneering work on lipoproteins has significantly shaped our current understanding of lipoprotein structure and dynamics. In addition to his research focus on LDL, Peter devoted a large part of his endeavor towards understanding complex biological membranes. Early on, he considered the membrane as a dynamic entity with spatial and temporal fluctuations in its local composition. So, he initiated structural studies on lipid polymorphism and domain formation, long before the term ‘‘membrane rafts’’ became popular. A particularly important study concerns the demonstration of chain interdigitated bilayers in ether-chain lipid membranes. He also pioneered lipid interactions with membrane-active peptides, showing that melittin from bee venom acts on membrane collective properties at concentrations as low as 1/1,000 (peptide/lipid molar ratio). G. Pabst (&) R. Prassl H. Amenitsch M. Rappolt K. Lohner Institute of Biophysics and Nanosystems Research, 8042 Graz, Austria e-mail: georg.pabst@oeaw.ac.at

Lamellar lipid structures are the fundamental structural motifs of biological membranes. To mimic this feature we have engineered short amphiphilic designer peptides with the aim to create peptide-based membrane analogs. As peptide scaffolds we have chosen six derivatives of V4WD2 - a peptide composed of four hydrophobic valine residues, followed by tryptophan and two negatively charged hydrophilic aspartic acid residues. The hydrophile-lipophile ratio, tryptophan content, and level of hydrophobicity have been systematically varied.

Apolipoprotein B100 (apoB100)-containing plasma lipoproteins (LDL and VLDL) supply tissues and cells with cholesterol and fat. During lipolytic conversion from VLDL to LDL the size and chemical composition of the particles change, but the apoB100 molecule remains bound to the lipids and regulates the receptor mediated uptake. The molecular physical parameters which control lipoprotein remodeling and enable particle stabilization by apoB100 are largely unknown. Here, we have compared the molecular dynamics and elasticities of VLDL and LDL derived by elastic neutron scattering temperature scans. We have determined thermal motions, dynamical transitions, and molecular fluctuations, which reflect the temperature-dependent motional coupling between lipid and protein. Our results revealed that lipoprotein particles are extremely soft and flexible. We found substantial differences in the molecular resiliences of lipoproteins, especially at higher temperatures. These discrepancies not only can be explained in terms of lipid composition and mobility but also suggest that apoB100 displays different dynamics dependent on the lipoprotein it is bound to. Hence, we suppose that the inherent conformational flexibility of apoB100 permits particle stabilization upon lipid exchange, whereas the dynamic coupling between protein and lipids might be a key determinant for lipoprotein conversion and atherogenicity.

Gunter Almer,1,* Kelli L Summers,1,2,* Bernhard Scheicher,2 Josef Kellner,3 Ingeborg Stelzer,1 Gerd Leitinger,4,5 Anna Gries,3 Ruth Prassl,6 Andreas Zimmer,2 Harald Mangge1,7 1Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria; 2Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology, University of Graz, Graz, Austria; 3Institute of Physiological Chemistry, Medical University of Graz, Graz, Austria; 4Research Unit Electron Microscopic Techniques, Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria; 5Center for Medical Research (ZMF), Medical University of Graz, Graz, Austria; 6Institute of Biophysics, Medical University of Graz, Graz, Austria; 7BioTechMed, Graz, Austria*These authors contributed equally to the study Abstract: Atherosclerosis (AS) is one of the leading causes of mortality in high-income countries. Early diagnosis of vulnerable atherosclerotic lesions is one of the biggest challenges currently facing cardiovascular medicine. The present study focuses on developing targeted nanoparticles (NPs) in order to improve the detection of vulnerable atherosclerotic-plaques. Various biomarkers involved in the pathogenesis of atherosclerotic-plaques have been identified and one of these promising candidates for diagnostic targeting is interleukin 10 (IL10). IL10 has been shown to be a key anti-inflammatory responding cytokine in the early stages of atherogenesis, and has already been used for therapeutic interventions in humans and mice. IL10, the targeting sequence, was coupled to two different types of NPs: protamine-oligonucleotide NPs (proticles) and sterically stabilized liposomes in order to address the question of whether the recognition and detection of atherosclerotic-lesions is primarily determined by the targeting sequence itself, or whether it depends on the NP carrier system to which the biomarker is coupled. Each IL10-targeted NP was assessed based on its sensitivity and selectivity toward characterizing atherosclerotic-plaque lesions using an apolipoprotein E-deficient mouse as the model of atherosclerosis. Aortas from apolipoprotein E-deficient mice fed a high fat diet, were stained with either fluorescence-labeled IL10 or IL10-coupled NPs. Ex vivo imaging was performed using confocal laser-scanning microscopy. We found that IL10-targeted proticles generated a stronger signal by accumulating at the surface of atherosclerotic-plaques, while IL10-targeted, sterically stabilized liposomes showed a staining pattern deeper in the plaque compared to the fluorescence-labeled IL10 alone. Our results point to a promising route for enhanced in vivo imaging using IL10-targeted NPs. NPs allow a higher payload of signal emitting molecules to be delivered to the atherosclerotic-plaques, thus improving signal detection. Importantly, this allows for the opportunity to visualize different areas within the plaque scenario, depending on the nature of the applied nanocarrier.Keywords: interleukin 10, atherosclerotic plaques, nanoparticles, proticles, liposomes

Self-assembling amphiphilic designer-peptides are used as building blocks for the development of controllable, tailor-made biomaterials. In solution, they self-assemble above a critical aggregation concentration into supramolecular structures, like vesicles, bilayers, twisted tapes, fibers or tubes. In this study we investigated the concentration- and time-dependent self-assembly of an 8-residue amphiphilic designer-peptide. We observed structural transitions from peptide monomers to elongated pairwise aligned tapes. Highly concentrated samples assembled into the first double helix superstructure that was observed within the class of amphiphilic designer-peptides so far. Synchrotron small angle X-ray scattering provided a detailed insight into the internal organization of the double helix. The obtained electron-density-profile suggested a 3-shell-model, mirrored at the central axis. Shell 1 (∼1 nm) and shell 2 (∼3.5 nm) together account for the peptide containing region, where the hydrophobic parts of the peptide monomers were interdigitated and tightly packed. In the innermost region we confirmed antiparallel stacking due to intermolecular hydrogen bonding by circular dichroism and infrared spectroscopy. Shell 3 spans around 12 nm and was assigned to a hydration shell where negatively charged trifluoroacetate counter ions preferably attach to the positively charged peptide headgroups. The total diameter of the double helix was 24 nm, with a repeating pitch distance of ∼60 nm. Cryo transmission electron microscopy supported the double helix morphology and revealed that their lengths extended to several hundreds of nanometers. The double helices were intertwined into a tight network. The resulting hydrogel properties may lead to promising future applications.

In an attempt to understand the multifunctional involvement of beta(2)-glycoprotein I (beta(2)GPI) in autoimmune diseases, thrombosis, atherosclerosis, and inflammatory processes, substantial interest is focused on the interaction of beta(2)GPI with negatively charged ligands, in particular, with acidic phospholipids. In this study, unilamellar vesicles composed of cardiolipin were used as in vitro membrane system to test and further refine a model of interaction based on the crystal structure of beta(2)GPI. The data suggest that beta(2)GPI anchors to the membrane surface with its hydrophobic loop adjacent to the positively charged lysine rich region in domain V. Subsequently, beta(2)GPI penetrates the membrane interfacial headgroup region as indicated by a restriction of the lipid side chain mobility, but without formation of a nonbilayer lipid phase. A structural rearrangement of beta(2)GPI upon lipid binding was detected by microcalorimetry and may result in the exposure of cryptic epitopes located in the complement control protein domains. This lipid-dependent conformational change may induce oligomerization of beta(2)GPI and promote intermolecular associations. Thus, the aggregation tendency of beta(2)GPI may serve as the basis for the formation of a molecular link between cells but may also be an essential feature for binding of autoantibodies and hence determine the role of beta(2)GPI in autoimmune diseases.

The influence of thermally induced changes in the lipid core structure on the oxidative resistance of discrete, homogeneous low density lipoprotein (LDL) subspecies (d, 1.0297-1.0327 and 1.0327-1.0358 g/ml) has been evaluated. The thermotropic transition of the LDL lipid core at temperatures between 15 degrees C and 37 degrees C, determined by differential scanning calorimetry, exerted significant effects on the kinetics of copper-mediated LDL oxidation expressed in terms of intrinsic antioxidant efficiency (lag time) and diene production rate. Thus, the temperature coefficients of oxidative resistance and maximum oxidation rate showed break points at the core transition temperature. Temperature-induced changes in copper binding were excluded as the molecular basis of such effects, as the saturation of LDL with copper was identical below and above the core transition. At temperatures below the transition, the elevation in lag time indicated a greater resistance to oxidation, reflecting a higher degree of antioxidant protection. This effect can be explained by higher motional constraints and local antioxidant concentrations, the latter resulting from the freezing out of antioxidants from crystalline domains of cholesteryl esters and triglycerides. Below the transition temperature, the conjugated diene production rate was decreased, a finding that correlated positively with the average size of the cooperative units of neutral lipids estimated from the calorimetric transition width. The reduced accessibility and structural hindrance in the cluster organization of the core lipids therefore inhibits peroxidation. Our findings provide evidence for a distinct effect of the dynamic state of the core lipids on the oxidative susceptibility of LDL and are therefore relevant to the atherogenicity of these cholesterol-rich particles.

Kerstin Gradauer,1 Caroline Vonach,1 Gerd Leitinger,2,3 Dagmar Kolb,2,3 Eleonore Fröhlich,3 Eva Roblegg,4 Andreas Bernkop-Schnürch,5 Ruth Prassl1,61Institute of Biophysics and Nanosystems Research, Austrian Academy of Sciences, Graz, Austria; 2Institute of Cell Biology, Histology, and Embryology, Medical University of Graz, Graz, Austria; 3Center for Medical Research, Medical University of Graz, Graz, Austria; 4Institute of Pharmaceutical Sciences/Pharmaceutical Technology, Karl-Franzens University, Graz, Austria; 5Department of Pharmaceutical Technology, Institute of Pharmacy, University of Innsbruck, Innsbruck, Austria; 6Ludwig Boltzmann Institute for Lung Vascular Research, Graz, AustriaAim: To develop mucoadhesive liposomes by anchoring the polymer chitosan-thioglycolic acid (chitosan-TGA) to the liposomal surface to target intestinal mucosal membranes.Methods: Liposomes consisting of phosphatidylcholine (POPC) and a maleimide-functionalized lipid were incubated with chitosan-TGA, leading to the formation of a thioether bond between free SH-groups of the polymer and maleimide groups of the liposome. Uncoated and newly generated thiomer-coated liposomes were characterized according to their size, zeta potential, and morphology using photon correlation spectroscopy and transmission electron microscopy. The release behavior of calcitonin and the fluorophore/quencher-couple ANTS/DPX (8-aminonaphthalene-1,3,6-trisulfonic acid/p-xylene-bis- pyridinium bromide) from coated and uncoated liposomes, was investigated over 24 hours in simulated gastric and intestinal fluids. To test the mucoadhesive properties of thiomer-coated and uncoated liposomes in-vitro, we used freshly excised porcine small intestine.Results: Liposomes showed a concentration-dependent increase in size – from approximately 167 nm for uncoated liposomes to 439 nm for the highest thiomer concentration used in this study. Likewise, their zeta potentials gradually increased from about –38 mV to +20 mV, clearly indicating an effective coupling of chitosan-TGA to the surface of liposomes. As a result of mucoadhesion tests, we found an almost two-fold increase in the mucoadhesion of coupled liposomes relative to uncoupled ones. With fluorescence microscopy, we saw a tight adherence of coated particles to the intestinal mucus.Conclusion: Taken together, our current results indicate that thiomer-coated liposomes possess a high potential to be used as an oral drug-delivery system.Keywords: thiomer, liposome, mucoadhesion, chitosan-thioglycolic acid, oral drug delivery

This review highlights recent advances in structural studies on low density lipoprotein (LDL) with particular emphasis on the apolipoprotein moiety of LDL, apolipoprotein B100 (apoB100). Various molecular aspects of LDL are outlined and obstacles to structure determination are addressed. In this context, the prevailing conceptions of the molecular assembly of LDL and how the synergy of complementary biochemical, biophysical and molecular simulation approaches has lead to the current structural model of LDL are discussed. Evidence is presented that structural heterogeneity and the intrinsic dynamics of LDL are key determinants of the functionality of LDL in both health and disease. Some key research directions, remaining open questions and rapidly emerging new concepts for medical applications of LDL, are furthermore outlined. The article concludes by providing an outlook concerning promising future strategies for the clarification of the molecular details of LDL, in particular of apoB100, combining recent advances in molecular modeling with developments of novel experimental techniques. Although new insights into the molecular organization of LDL are forthcoming, many open questions remain unanswered. The major challenge of the next decade will certainly be the elucidation of the molecular structural and dynamic features of apoB100.

A polymer-grafted liposomal formulation that has the potential to be developed for aerosolic pulmonary delivery of vasoactive intestinal peptide (VIP), a potent vasodilatory neuropeptide, is described. As VIP is prone to rapid proteolytic degradation in the microenvironment of the lung a proper delivery system is required to increase the half-life and bioavailability of the peptide. Here we investigate structural parameters of unilamellar liposomes composed of palmitoyl-oleoyl-phosphatidylcholine, lyso-stearyl-phosphatidylglycerol and distearyl-phosphatidyl-ethanolamine covalently linked to polyethylene glycol 2000, and report on VIP–lipid interaction mechanisms. We found that the cationic VIP is efficiently entrapped by the negatively charged spherical liposomes and becomes converted to an amphipathic α-helix. By fluorescence spectroscopy using single Trp-modified VIP we could show that VIP is closely associated to the membrane. Our data suggest that the N-terminal random-coiled domain is embedded in the interfacial headgroup region of the phospholipid bilayer. By doing so, neither the bilayer thickness of the lipid membrane nor the mobility of the phospholipid acyl chains are affected as shown by small angle X-ray scattering and electron spin resonance spectroscopy. Finally, in an ex vivo lung arterial model system we found that liposomal-associated VIP is recognized by its receptors to induce vasodilatory effects with comparable high relaxation efficiency as free VIP but with a significantly retarded dilatation kinetics. In conclusion, we have designed and characterized a liposomal formulation that is qualified to entrap biologically active VIP and displays structural features to be considered for delivery of VIP to the lung.

Pritesh P Jain,1 Regina Leber,1,2 Chandran Nagaraj,1 Gerd Leitinger,3 Bernhard Lehofer,4 Horst Olschewski,1,5 Andrea Olschewski,1,6 Ruth Prassl,1,4 Leigh M Marsh11Ludwig Boltzmann Institute for Lung Vascular Research, 2Biophysics Division, Institute of Molecular Biosciences, University of Graz, 3Research Unit Electron Microscopic Techniques, Institute of Cell Biology, Histology, and Embryology, 4Institute of Biophysics, 5Division of Pulmonology, Department of Internal Medicine, 6Department of Anesthesiology and Intensive Care Medicine, Medical University of Graz, Graz, AustriaAbstract: Prostacyclin analogues are standard therapeutic options for vasoconstrictive diseases, including pulmonary hypertension and Raynaud’s phenomenon. Although effective, these treatment strategies are expensive and have several side effects. To improve drug efficiency, we tested liposomal nanoparticles as carrier systems. In this study, we synthesized liposomal nanoparticles tailored for the prostacyclin analogue iloprost and evaluated their pharmacologic efficacy on mouse intrapulmonary arteries, using a wire myograph. The use of cationic lipids, stearylamine, or 1,2-di-(9Z-octadecenoyl)-3-trimethylammonium-propane (DOTAP) in liposomes promoted iloprost encapsulation to at least 50%. The addition of cholesterol modestly reduced iloprost encapsulation. The liposomal nanoparticle formulations were tested for toxicity and pharmacologic efficacy in vivo and ex vivo, respectively. The liposomes did not affect the viability of human pulmonary artery smooth muscle cells. Compared with an equivalent concentration of free iloprost, four out of the six polymer-coated liposomal formulations exhibited significantly enhanced vasodilation of mouse pulmonary arteries. Iloprost that was encapsulated in liposomes containing the polymer polyethylene glycol exhibited concentration-dependent relaxation of arteries. Strikingly, half the concentration of iloprost in liposomes elicited similar pharmacologic efficacy as nonencapsulated iloprost. Cationic liposomes can encapsulate iloprost with high efficacy and can serve as potential iloprost carriers to improve its therapeutic efficacy.Keywords: prostacyclin, cationic liposomes, pulmonary hypertension, wire myograph

The interactions of the lipid and protein moiety of human low-density lipoprotein (LDL) and their influence on the oxidation behavior of LDL were modified using an amphipathic peptide, melittin, as a probe. The interaction of melittin with the LDL phospholipid surface resulted in a destabilization of apolipoprotein B-100 (apoB-100) as monitored by differential scanning calorimetry, while the characteristics of lipid core melting remained nearly unchanged. Binding of melittin caused a restriction of lipid chain mobility near the glycerol backbone, but not in the middle or near the methyl terminus of the fatty acyl chains as observed by electron paramagnetic resonance. Also, upon melittin addition, the level of copper binding to apoB-100 and the oxidizability of LDL by Cu2+ ions were greatly reduced, as indicated by abolished tryptophan fluorescence quenching upon Cu2+ binding and, during oxidation, prolongation of the lag phase of oxidation, attenuated consumption of alpha-tocopherol, and a lowered maximal rate of conjugated diene formation. This reduction of oxidizability could not be reversed by increasing the Cu2+ concentration. It is deduced that interaction of Cu2+ and alpha-tocopherol is required for reductive activation of the metal. It can be abolished by interfering with the interactions between apoB-100 and the lipid moiety of LDL which modifies the conformation of LDL and, as a consequence, hinders copper binding to apoB-100.

The time course of the unfolding characteristics of the protein moiety and of the thermotropic behavior of the core-located apolar lipids of highly homogeneous low-density lipoprotein (LDL) subspecies (d 1.030-1.040 g/mL) have been evaluated during transition metal- and azo radical-induced oxidation using differential scanning calorimetry. Apolipoprotein B100 (apo-B100) structure was highly sensitive to oxidative modification; indeed, a significant loss of thermal stability was observed at initial stages irrespective of whether oxidation was mediated by site-specific binding of copper ions or by free radicals generated during decomposition of azo compounds. Subsequently, thermal protein integrity was destroyed, as a result of potentially irreversible protein unfolding, cross-linking reactions, and aggregation. Our results suggest that even minimal oxidative modification of apo-B100 has a major impact on the stability of this large monomeric protein. By contrast, the core lipids, which consist primarily of cholesteryl esters and triglycerides and play a determinant role in the thermal transition occurring near physiological temperature, preserved features of an ordered arrangement even during propagation of lipid peroxidation.

Christine Rangger,1 Anna Helbok,1 Jane Sosabowski,2 Christian Kremser,3 Gottfried Koehler,4 Ruth Prassl,5,6 Fritz Andreae,7 Irene J Virgolini,1 Elisabeth von Guggenberg,1 Clemens Decristoforo11Department of Nuclear Medicine, Innsbruck Medical University, Innsbruck, Austria; 2Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, London, UK; 3Department of Radiology, Innsbruck Medical University, Innsbruck, 4Department of Computational and Structural Biology, Max Perutz Laboratories, University of Vienna, Wien, 5Institute of Biophysics, Medical University of Graz, Graz, 6Ludwig Boltzmann Institute for Lung Vascular Research, 7piCHEM Research and Development, Graz, AustriaBackground: The significant progress in nanotechnology provides a wide spectrum of nanosized material for various applications, including tumor targeting and molecular imaging. The aim of this study was to evaluate multifunctional liposomal nanoparticles for targeting approaches and detection of tumors using different imaging modalities. The concept of dual-targeting was tested in vitro and in vivo using liposomes derivatized with an arginine-glycine-aspartic acid (RGD) peptide binding to αvβ3 integrin receptors and a substance P peptide binding to neurokinin-1 receptors.Methods: For liposome preparation, lipids, polyethylene glycol building blocks, DTPA-derivatized lipids for radiolabeling, lipid-based RGD and substance P building blocks and imaging labels were combined in defined molar ratios. Liposomes were characterized by photon correlation spectroscopy and zeta potential measurements, and in vitro binding properties were tested using fluorescence microscopy. Standardized protocols for radiolabeling were developed to perform biodistribution and micro-single photon emission computed tomography/computed tomography (SPECT/CT) studies in nude mice bearing glioblastoma and/or melanoma tumor xenografts. Additionally, an initial magnetic resonance imaging study was performed.Results: Liposomes were radiolabeled with high radiochemical yields. Fluorescence microscopy showed specific cellular interactions with RGD-liposomes and substance P-liposomes. Biodistribution and micro-SPECT/CT imaging of 111In-labeled liposomal nanoparticles revealed low tumor uptake, but in a preliminary magnetic resonance imaging study with a single-targeted RGD-liposome, uptake in the tumor xenografts could be visualized.Conclusion: The present study shows the potential of liposomes as multifunctional targeted vehicles for imaging of tumors combining radioactive, fluorescent, and magnetic resonance signaling. Specific in vitro tumor targeting by fluorescence microscopy and radioactivity was achieved. However, biodistribution studies in an animal tumor model revealed only moderate tumor uptake and no additive effect using a dual-targeting approach.Keywords: liposomal nanoparticles, radiolabeling, dual-targeting, tumor imaging, multifunctionality

Background The potential physiological significance of the nanophase transition of neutral lipids in the core of low density lipoprotein (LDL) particles is dependent on whether the rate is fast enough to integrate small (±2°C) temperature changes in the blood circulation. Methodology/Principal Findings Using sub-second, time-resolved small-angle X-ray scattering technology with synchrotron radiation, we have monitored the dynamics of structural changes within LDL, which were triggered by temperature-jumps and -drops, respectively. Our findings reveal that the melting transition is complete within less than 10 milliseconds. The freezing transition proceeds slowly with a half-time of approximately two seconds. Thus, the time period over which LDL particles reside in cooler regions of the body readily facilitates structural reorientation of the apolar core lipids. Conclusions/Significance Low density lipoproteins, the biological nanoparticles responsible for the transport of cholesterol in blood, are shown to act as intrinsic nano-thermometers, which can follow the periodic temperature changes during blood circulation. Our results demonstrate that the lipid core in LDL changes from a liquid crystalline to an oily state within fractions of seconds. This may, through the coupling to the protein structure of LDL, have important repercussions on current theories of the role of LDL in the pathogenesis of atherosclerosis.

Apolipoprotein B100 (apoB100)-containing lipoproteins (very low density lipoprotein (VLDL) and low density lipoprotein (LDL)) are the principal fat and cholesterol carriers in blood. During metabolic conversion from VLDL to LDL, the particle size decreases (from ∼ 80 nm to 20 nm) and lipid composition is changed, however, the amphiphilic apoB100 molecule remains bound to its lipoprotein particle and most likely compensates for structural changes due to its inherent conformational flexibility and dynamics .Here, we report on motions in the time range of 100 ps to 1 ns in human-LDL, human VLDL and yolk-VLDL, which were recorded by elastic neutron-scattering temperature scans from 20K to 310 K using hydrated lipoprotein powders. The mean square displacement values were calculated from the scattering vector dependence of the elastic intensity I(Q). The effective force constants , which are a measure for the resilience of the particle, were derived from the slopes in the vs. T scans. In the low-temperature harmonic regime we found no substantial differences between lipoprotein fractions ( ∼1 N/m). Nevertheless, lipoproteins are softer compared to hydrated myoglobin powder (2 N/m) or purple membranes (1.7 N/m) [1]. Significant differences were observed with increasing temperatures. Both, human and yolk VLDL show two breaks in the scan with a steep increase in above 270K, whereas LDL shows a smooth behavior above a dynamic transition around 220K. Accordingly, at physiological temperatures VLDL-fractions are highly soft and mobile ( ∼0.08 N/m) as compared to LDL ( ∼ 0.2 N/m). Sucrose, added as cryoprotectant, significantly modified the dynamics of VLDL, as it confers extreme stability to VLDL over the whole temperature range and substantially suppresses dynamic transitions.[1] G. Zaccai, Science 288 (2000), 1604-1607