lipid order Dotaz Zobrazit nápovědu
BACKGROUND AND PURPOSE: Although the amphiphilic nature of the widely used antithrombotic drug Ticagrelor is well known, it was never considered as a membranotropic agent capable of interacting with the lipid bilayer in a receptor-independent way. In this study, we investigated the influence of Ticagrelor on plasma membrane lipid order in platelets and if this modulates the potency of Ticagrelor at the P2Y12 receptor. EXPERIMENTAL APPROACH: We combined fluorescent in situ, in vitro and in silico approaches to probe the interactions between the plasma membrane of platelets and Ticagrelor. The influence of Ticagrelor on the lipid order of the platelet plasma membrane and large unilamellar vesicles was studied using the advanced fluorescent probe NR12S. Furthermore, the properties of model lipid bilayers in the presence of Ticagrelor were characterized by molecular dynamics simulations. Finally, the influence of an increased lipid order on the dose-response of platelets to Ticagrelor was studied. KEY RESULTS: Ticagrelor incorporates spontaneously into lipid bilayers and affects the lipid order of the membranes of model vesicles and isolated platelets, in a nontrivial composition and concentration-dependent manner. We showed that higher plasma membrane lipid order in platelets leads to a lower IC50 value for Ticagrelor. It is shown that membrane incorporation of Ticagrelor increases its potency at the P2Y12 receptor, by increasing the order of the platelet plasma membrane. CONCLUSION AND IMPLICATIONS: A novel dual mechanism of Ticagrelor action is suggested that combines direct binding to P2Y12 receptor with simultaneous modulation of receptor-lipid microenvironment.
- MeSH
- buněčná membrána * účinky léků metabolismus MeSH
- lidé MeSH
- lipidové dvojvrstvy metabolismus MeSH
- membránové lipidy metabolismus MeSH
- purinergní receptory P2Y - antagonisté farmakologie chemie MeSH
- purinergní receptory P2Y12 * metabolismus účinky léků MeSH
- simulace molekulární dynamiky MeSH
- ticagrelor * farmakologie chemie MeSH
- trombocyty * účinky léků metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
We addressed the onset of synergistic activity of the two well-studied antimicrobial peptides magainin 2 (MG2a) and PGLa using lipid-only mimics of Gram-negative cytoplasmic membranes. Specifically, we coupled a joint analysis of small-angle x-ray and neutron scattering experiments on fully hydrated lipid vesicles in the presence of MG2a and L18W-PGLa to all-atom and coarse-grained molecular dynamics simulations. In agreement with previous studies, both peptides, as well as their equimolar mixture, were found to remain upon adsorption in a surface-aligned topology and to induce significant membrane perturbation, as evidenced by membrane thinning and hydrocarbon order parameter changes in the vicinity of the inserted peptide. These effects were particularly pronounced for the so-called synergistic mixture of 1:1 (mol/mol) L18W-PGLa/MG2a and cannot be accounted for by a linear combination of the membrane perturbations of two peptides individually. Our data are consistent with the formation of parallel heterodimers at concentrations below a synergistic increase of dye leakage from vesicles. Our simulations further show that the heterodimers interact via salt bridges and hydrophobic forces, which apparently makes them more stable than putatively formed antiparallel L18W-PGLa and MG2a homodimers. Moreover, dimerization of L18W-PGLa and MG2a leads to a relocation of the peptides within the lipid headgroup region as compared to the individual peptides. The early onset of dimerization of L18W-PGLa and MG2a at low peptide concentrations consequently appears to be key to their synergistic dye-releasing activity from lipid vesicles at high concentrations.
- MeSH
- buněčná membrána metabolismus MeSH
- dimerizace MeSH
- fosfatidylethanolaminy MeSH
- fosfatidylglyceroly MeSH
- kationické antimikrobiální peptidy metabolismus MeSH
- lipidové dvojvrstvy chemie MeSH
- lipidy chemie MeSH
- magaininy metabolismus MeSH
- simulace molekulární dynamiky MeSH
- teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Atherosclerotic cardiovascular disease (ASCVD) and consequent acute coronary syndromes (ACS) are substantial contributors to morbidity and mortality across Europe. Much of these diseases burden is modifiable, in particular by lipid-lowering therapy (LLT). Current guidelines are based on the sound premise that with respect to low density lipoprotein cholesterol (LDL-C), "lower is better for longer", and the recent data have strongly emphasized the need of also "the earlier the better". In addition to statins, which have been available for several decades, the availability of ezetimibe and inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9) are additional very effective approach to LLT, especially for those at very high and extremely high cardiovascular risk. LLT is initiated as a response to an individual's calculated risk of future ASCVD and is intensified over time in order to meet treatment goals. However, in real-life clinical practice goals are not met in a substantial proportion of patients. This Position Paper complements existing guidelines on the management of lipids in patients following ACS. Bearing in mind the very high risk of further events in ACS, we propose practical solutions focusing on immediate combination therapy in strict clinical scenarios, to improve access and adherence to LLT in these patients. We also define an 'Extremely High Risk' group of individuals following ACS, completing the attempt made in the recent European guidelines, and suggest mechanisms to urgently address lipid-medicated cardiovascular risk in these patients.
- MeSH
- akutní koronární syndrom krev farmakoterapie MeSH
- anticholesteremika škodlivé účinky terapeutické užití MeSH
- ateroskleróza krev farmakoterapie MeSH
- ezetimib škodlivé účinky terapeutické užití MeSH
- lidé MeSH
- lipidy krev MeSH
- management nemoci MeSH
- PCSK9 inhibitory škodlivé účinky terapeutické užití MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Ceramides (Cers) with ultralong (∼32-carbon) chains and ω-esterified linoleic acid, composing a subclass called omega-O-acylceramides (acylCers), are indispensable components of the skin barrier. Normal barriers typically contain acylCer concentrations of ∼10 mol%; diminished concentrations, along with altered or missing long periodicity lamellar phase (LPP), and increased permeability accompany an array of skin disorders, including atopic dermatitis, psoriasis, and ichthyoses. We developed model membranes to investigate the effects of the acylCer structure and concentration on skin lipid organization and permeability. The model membrane systems contained six to nine Cer subclasses as well as fatty acids, cholesterol, and cholesterol sulfate; acylCer content-namely, acylCers containing sphingosine (Cer EOS), dihydrosphingosine (Cer EOdS), and phytosphingosine (Cer EOP) ranged from zero to 30 mol%. Systems with normal physiologic concentrations of acylCer mixture mimicked the permeability and nanostructure of human skin lipids (with regard to LPP, chain order, and lateral packing). The models also showed that the sphingoid base in acylCer significantly affects the membrane architecture and permeability and that Cer EOP, notably, is a weaker barrier component than Cer EOS and Cer EOdS. Membranes with diminished or missing acylCers displayed some of the hallmarks of diseased skin lipid barriers (i.e., lack of LPP, less ordered lipids, less orthorhombic chain packing, and increased permeability). These results could inform the rational design of new and improved strategies for the barrier-targeted treatment of skin diseases.
Cholesterol is important for the formation of microdomains in supported lipid bilayers and is enriched in the liquid-ordered phase. To understand the interactions leading to this enrichment, we developed an AFM-based single-lipid-extraction (SLX) approach that enables us to determine the anchoring strength of cholesterol in the two phases of a phase-separated lipid membrane. As expected, the forces necessary for extracting a single cholesterol molecule from liquid-ordered phases are significantly higher than for extracting it from the liquid-disordered phases. Interestingly, application of the Bell model shows two energy barriers that correlate with the head and full length of the cholesterol molecule. The resulting lifetimes for complete extraction are 90 s and 11 s in the liquid-ordered and liquid-disordered phases, respectively. Molecular dynamics simulations of the very same experiment show similar force profiles and indicate that the stabilization of cholesterol in the liquid-ordered phase is mainly due to nonpolar contacts.
- MeSH
- cholesterol chemie MeSH
- fosfatidylcholiny chemie MeSH
- fosfatidylethanolaminy chemie MeSH
- lipidové dvojvrstvy chemie MeSH
- mikroskopie atomárních sil metody MeSH
- simulace molekulární dynamiky MeSH
- spektrální analýza MeSH
- unilamelární lipozómy chemie MeSH
- vodíková vazba MeSH
- změna skupenství MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Free radical scavengers like α-phenyl-N-tert-butylnitrone (PBN) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) have been widely used as protective agents in various biomimetic and biological models. A series of three amphiphilic Trolox and PBN derivatives have been designed by adding to those molecules a perfluorinated chain as well as a sugar group in order to render them amphiphilic. In this work, we have studied the interactions between these derivatives and lipid membranes to understand how they influence their ability to prevent membrane lipid oxidation. We showed the derivatives better inhibited the AAPH-induced oxidation of 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLiPC) small unilamellar vesicles (SUVs) than the parent compounds. One of the derivatives, bearing both PBN and Trolox moieties on the same fluorinated carrier, exhibited a synergistic antioxidant effect by delaying the oxidation process. We next investigated the ability of the derivatives to interact with DLiPC membranes in order to better understand the differences observed regarding the antioxidant properties. Surface tension and fluorescence spectroscopy experiments revealed the derivatives exhibited the ability to form monolayers at the air/water interface and spontaneously penetrated lipid membranes, underlying pronounced hydrophobic properties in comparison to the parent compounds. We observed a correlation between the hydrophobic properties, the depth of penetration and the antioxidant properties and showed that the location of these derivatives in the membrane is a key parameter to rationalize their antioxidant efficiency. Molecular dynamics (MD) simulations supported the understanding of the mechanism of action, highlighting various key physical-chemical descriptors.
- MeSH
- antioxidancia farmakologie MeSH
- chromany (dihydrobenzopyrany) chemie MeSH
- fluor chemie MeSH
- membránové lipidy chemie MeSH
- membrány umělé MeSH
- oxidace-redukce MeSH
- oxidy dusíku chemie MeSH
- peroxidace lipidů MeSH
- synergismus léků MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
We study how lipid probes based on pyrene-labeling could be designed to minimize perturbations in lipid bilayers, and how the same design principles could be exploited to develop probes which gauge lipid dynamics primarily within a single lipid monolayer or between them. To this end, we use atomistic molecular dynamics simulations to consider membranes where pyrene moieties are attached to lipid acyl chains in varying positions. We find that in a DOPC bilayer the conformational ordering of lipids around di-pyrenyl-PC probes is altered to a largely similar extent regardless of where the pyrene moiety is attached to the hydrocarbon chain. This is in contrast to saturated membranes, where pyrene-induced perturbations have been observed to be more prominent. Meanwhile, the formation of pyrene dimers depends on the linkage point between pyrene and its host lipid. Membrane-spanning dimers between lipids in different membrane leaflets are observed only if the pyrene moiety is attached to the latter half of the acyl chain. A seemingly minor change to link pyrene to an acyl chain that is two carbons shorter leads to a situation where membrane-spanning dimers are no longer observed. Further, simulations suggest that formation of dimers is a slow process, where the rate is limited by both lateral diffusion and the dimerization process once the two probes are neighbors to one another. Typical lifetimes of pyrene dimers turn out be of the order of nanoseconds. The results are expected to pave the way for designing ways to consider experimentally topics such as intraleaflet lateral diffusion, motion of lipids within and between membrane domains, and membrane domain registration across bilayers.
- MeSH
- buněčná membrána chemie účinky léků MeSH
- časové faktory MeSH
- dimerizace * MeSH
- fluorescenční barviva chemie farmakologie MeSH
- lipidové dvojvrstvy chemie MeSH
- membránové lipidy chemie MeSH
- pyreny chemie farmakologie MeSH
- uhlovodíky chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
In Part I, by using 31P-NMR spectroscopy, we have shown that isolated granum and stroma thylakoid membranes (TMs), in addition to the bilayer, display two isotropic phases and an inverted hexagonal (HII) phase; saturation transfer experiments and selective effects of lipase and thermal treatments have shown that these phases arise from distinct, yet interconnectable structural entities. To obtain information on the functional roles and origin of the different lipid phases, here we performed spectroscopic measurements and inspected the ultrastructure of these TM fragments. Circular dichroism, 77 K fluorescence emission spectroscopy, and variable chlorophyll-a fluorescence measurements revealed only minor lipase- or thermally induced changes in the photosynthetic machinery. Electrochromic absorbance transients showed that the TM fragments were re-sealed, and the vesicles largely retained their impermeabilities after lipase treatments-in line with the low susceptibility of the bilayer against the same treatment, as reflected by our 31P-NMR spectroscopy. Signatures of HII-phase could not be discerned with small-angle X-ray scattering-but traces of HII structures, without long-range order, were found by freeze-fracture electron microscopy (FF-EM) and cryo-electron tomography (CET). EM and CET images also revealed the presence of small vesicles and fusion of membrane particles, which might account for one of the isotropic phases. Interaction of VDE (violaxanthin de-epoxidase, detected by Western blot technique in both membrane fragments) with TM lipids might account for the other isotropic phase. In general, non-bilayer lipids are proposed to play role in the self-assembly of the highly organized yet dynamic TM network in chloroplasts.
The myelin sheath is an essential, multilayered membrane structure that insulates axons, enabling the rapid transmission of nerve impulses. The tetraspan myelin proteolipid protein (PLP) is the most abundant protein of compact myelin in the central nervous system (CNS). The integral membrane protein PLP adheres myelin membranes together and enhances the compaction of myelin, having a fundamental role in myelin stability and axonal support. PLP is linked to severe CNS neuropathies, including inherited Pelizaeus-Merzbacher disease and spastic paraplegia type 2, as well as multiple sclerosis. Nevertheless, the structure, lipid interaction properties, and membrane organization mechanisms of PLP have remained unidentified. We expressed, purified, and structurally characterized human PLP and its shorter isoform DM20. Synchrotron radiation circular dichroism spectroscopy and small-angle X-ray and neutron scattering revealed a dimeric, α-helical conformation for both PLP and DM20 in detergent complexes, and pinpoint structural variations between the isoforms and their influence on protein function. In phosphatidylcholine membranes, reconstituted PLP and DM20 spontaneously induced formation of multilamellar myelin-like membrane assemblies. Cholesterol and sphingomyelin enhanced the membrane organization but were not crucial for membrane stacking. Electron cryomicroscopy, atomic force microscopy, and X-ray diffraction experiments for membrane-embedded PLP/DM20 illustrated effective membrane stacking and ordered organization of membrane assemblies with a repeat distance in line with CNS myelin. Our results shed light on the 3D structure of myelin PLP and DM20, their structure-function differences, as well as fundamental protein-lipid interplay in CNS compact myelin.
- MeSH
- axony metabolismus MeSH
- centrální nervový systém metabolismus MeSH
- lidé MeSH
- lipidové dvojvrstvy * metabolismus MeSH
- myelinová pochva metabolismus MeSH
- myelinový proteolipidový protein * metabolismus MeSH
- protein - isoformy metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
