RESUMEN
The interaction of L-Phe with the membrane components, i.e., lipids and proteins, has been discussed in the current literature due to the interest to understand the effect of single amino acids in relation to the formation of amyloid aggregates. In the present work, it is shown that L-Phe interacts with 9:1 DMPC (1,2-dimyristoyl-sn-glycero-3 phosphocholine)/DPPC (1,2-dipalmitoyl-sn-glycero-3 phosphocholine) mixtures but not in the 1:9 one. An important observation is that the interaction disappears when DPPC is replaced by diether PC (2-di-O-hexadecyl-sn-glycero-3-phosphocholine) a lipid lacking carbonyl groups (CO). This denotes that CO groups may interact specifically with L-Phe in accordance with the appearance of a new peak observed by Infrared spectroscopy (FTIR-ATR). The interaction of L-Phe affects the compressibility pattern of the 9:1 DMPC/DPPC mixture which is congruent with the changes observed by Raman spectra. The specific interaction of L-Phe with CO, propagates to phosphate and choline groups in this particular mixture as analyzed by FTIR-ATR spectroscopy and is absent when DMPC is dopped with diether PC.
Asunto(s)
Dimiristoilfosfatidilcolina , Fenilalanina , Fenilalanina/química , Fenilalanina/metabolismo , Dimiristoilfosfatidilcolina/química , Espectroscopía Infrarroja por Transformada de Fourier , Membrana Dobles de Lípidos/química , Membrana Dobles de Lípidos/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Lípidos de la Membrana/química , Lípidos de la Membrana/metabolismoRESUMEN
Understanding the transport mechanism of the peptide Asn-Cys-Trp (NCW) is crucial to improving its intestinal absorption and bioavailability. This study investigated the absorption of NCW through Caco-2 cell monolayers and its interaction with the DPPC bilayers. Results revealed that after a 3 h incubation, the Papp (AP-BL) and Papp (BL-AP) values of NCW at a concentration of 5 mmol/L were (22.24 ± 4.52) × 10-7 and (6.63 ± 2.31) × 10-7 cm/s, respectively, with the transport rates of 1.59 ± 0.32 and 0.62 ± 0.20%, indicating its moderate absorption. NCW was found to be transported via PepT1 and paracellular transport pathways, as evidenced by the significant impact of Gly-Pro and cytochalasin D on the Papp values. Moreover, NCW upregulated ZO-1 mRNA expression. Further investigation of the ZO-1-mediated interaction between NCW and tight junction proteins will contribute to a better understanding of the paracellular transport mechanism of NCW. The interaction between NCW and the DPPC bilayers was predominantly driven by entropy. NCW permeated the bilayers through electrostatic, hydrogen bonding, and hydrophobic interactions, resulting in increased fluidity, flexibility, and disorder as well as phase transition and phase separation of the bilayers.
Asunto(s)
Antihipertensivos , Humanos , Células CACO-2 , Transporte Biológico , Antihipertensivos/química , Antihipertensivos/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Difusión , Proteína de la Zonula Occludens-1/metabolismo , Proteína de la Zonula Occludens-1/genética , Oligopéptidos/química , Oligopéptidos/metabolismo , Membrana Dobles de Lípidos/química , Membrana Dobles de Lípidos/metabolismoRESUMEN
Adaptation to hypoxia has attracted much public interest because of its clinical significance. However, hypoxic adaptation in the body is complicated and difficult to fully explore. To explore previously unknown conserved mechanisms and key proteins involved in hypoxic adaptation in different species, we first used a yeast model for mechanistic screening. Further multi-omics analyses in multiple species including yeast, zebrafish and mice revealed that glycerophospholipid metabolism was significantly involved in hypoxic adaptation with up-regulation of lysophospholipid acyltransferase (ALE1) in yeast, a key protein for the formation of dipalmitoyl phosphatidylcholine [DPPC (16:0/16:0)], which is a saturated phosphatidylcholine. Importantly, a mammalian homolog of ALE1, lysophosphatidylcholine acyltransferase 1 (LPCAT1), enhanced DPPC levels at the cell membrane and exhibited the same protective effect in mammalian cells under hypoxic conditions. DPPC supplementation effectively attenuated growth restriction, maintained cell membrane integrity and increased the expression of epidermal growth factor receptor under hypoxic conditions, but unsaturated phosphatidylcholine did not. In agreement with these findings, DPPC treatment could also repair hypoxic injury of intestinal mucosa in mice. Taken together, ALE1/LPCAT1-mediated DPPC formation, a key pathway of glycerophospholipid metabolism, is crucial for cell viability under hypoxic conditions. Moreover, we found that ALE1 was also involved in glycolysis to maintain sufficient survival conditions for yeast. The present study offers a novel approach to understanding lipid metabolism under hypoxia and provides new insights into treating hypoxia-related diseases.
Asunto(s)
1-Acilglicerofosfocolina O-Aciltransferasa , Membrana Celular , Glicerofosfolípidos , Animales , Humanos , Ratones , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/química , 1-Acilglicerofosfocolina O-Aciltransferasa/metabolismo , 1-Acilglicerofosfocolina O-Aciltransferasa/genética , Adaptación Fisiológica/genética , Membrana Celular/metabolismo , Glicerofosfolípidos/metabolismo , Hipoxia/metabolismo , Hipoxia/genética , Mucosa Intestinal/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/crecimiento & desarrollo , Pez Cebra/metabolismo , Pez Cebra/genéticaRESUMEN
The size, dispersibility, and fluidity of DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine), POPC (1-palmitoy-2-oleoyl-sn-glycero-3-phosphocholine), and DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) liposomes doped with ß-sitosteryl sulfate (PSO4) were comparatively studied. In all three types of liposomes, PSO4 reduced sizes and enhanced the negative values of the ζ-potential. However, the effect on sizes quantitatively differed in the three cases in a manner dependent on their phase behaviors. PSO4 rigidified each type of membrane in its liquid crystalline phase and fluidized the gel phase. It enhanced the glucose trapping efficiency (TE) of both DPPC and DOPC liposomes. The TE of DPPC first increased with the increasing concentration of PSO4, then decreased gradually. On the other hand, in the case of DOPC, the TE increased significantly upon addition of PSO4, then remained nearly constant. Though the exact dependence of TE on the PSO4 concentration differed in the two cases, its effect, in each case, was more than the effect of ß-sitosterol (POH). The ability of PSO4 for reducing the size and enhancing dispersibility and TE of liposomes can be useful for preparing cosmetics and pharmaceutical formulations.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/química , Liposomas/química , Fosfatidilcolinas/química , Sitoesteroles/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Glucosa/metabolismo , Liposomas/metabolismo , Fluidez de la Membrana , Estructura Molecular , Tamaño de la Partícula , Fosfatidilcolinas/metabolismo , Sitoesteroles/metabolismo , Electricidad EstáticaRESUMEN
Vital biological processes, such as trafficking, sensing, and motility, are facilitated by cellular lipid membranes, which interact mechanically with surrounding fluids. Such lipid membranes are only a few nanometers thick and composed of a liquid crystalline structure known as the lipid bilayer. Here, we introduce an active, noncontact, two-point microrheology technique combining multiple optical tweezers probes with planar freestanding lipid bilayers accessible on both sides. We use the method to quantify both fluid slip close to the bilayer surface and transmission of fluid flow across the structure, and we use numerical simulations to determine the monolayer viscosity and the intermonolayer friction. We find that these physical properties are highly dependent on the molecular structure of the lipids in the bilayer. We compare ordered-phase with liquid disordered-phase lipid bilayers, and we find the ordered-phase bilayers to be 10 to 100 times more viscous but with 100 times less intermonolayer friction. When a local shear is applied by the optical tweezers, the ultralow intermonolayer friction results in full slip of the two leaflets relative to each other and as a consequence, no shear transmission across the membrane. Our study sheds light on the physical principles governing the transfer of shear forces by and through lipid membranes, which underpin cell behavior and homeostasis.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/química , Membrana Celular/química , Membrana Dobles de Lípidos/química , Lípidos de la Membrana/química , Fosfatidilcolinas/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Fenómenos Biomecánicos , Membrana Celular/metabolismo , Fricción , Hidrodinámica , Dispositivos Laboratorio en un Chip , Membrana Dobles de Lípidos/metabolismo , Lípidos de la Membrana/metabolismo , Pinzas Ópticas , Fosfatidilcolinas/metabolismo , Reología , Propiedades de Superficie , ViscosidadRESUMEN
The interactions at the atomic level between small molecules and the main components of cellular plasma membranes are crucial for elucidating the mechanisms allowing for the entrance of such small species inside the cell. We have performed molecular dynamics and metadynamics simulations of tryptophan, serotonin, and melatonin at the interface of zwitterionic phospholipid bilayers. In this work, we will review recent computer simulation developments and report microscopic properties, such as the area per lipid and thickness of the membranes, atomic radial distribution functions, angular orientations, and free energy landscapes of small molecule binding to the membrane. Cholesterol affects the behaviour of the small molecules, which are mainly buried in the interfacial regions. We have observed a competition between the binding of small molecules to phospholipids and cholesterol through lipidic hydrogen-bonds. Free energy barriers that are associated to translational and orientational changes of melatonin have been found to be between 10-20 kJ/mol for distances of 1 nm between melatonin and the center of the membrane. Corresponding barriers for tryptophan and serotonin that are obtained from reversible work methods are of the order of 10 kJ/mol and reveal strong hydrogen bonding between such species and specific phospholipid sites. The diffusion of tryptophan and melatonin is of the order of 10-7 cm2/s for the cholesterol-free and cholesterol-rich setups.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/química , Colesterol/química , Dimiristoilfosfatidilcolina/química , Melatonina/química , Serotonina/química , Triptófano/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Colesterol/metabolismo , Dimiristoilfosfatidilcolina/metabolismo , Enlace de Hidrógeno , Membrana Dobles de Lípidos/química , Membrana Dobles de Lípidos/metabolismo , Melatonina/metabolismo , Simulación de Dinámica Molecular , Serotonina/metabolismo , Soluciones , Electricidad Estática , Termodinámica , Triptófano/metabolismo , Agua/químicaRESUMEN
Carbon-based nanomaterials are nowadays attracting lots of attention, in particular in the biomedical field, where they find a wide spectrum of applications, including, just to name a few, the drug delivery to specific tumor cells and the improvement of non-invasive imaging methods. Nanoparticles inhaled during breathing accumulate in the lung alveoli, where they interact and are covered with lung surfactants. We recently demonstrated that an apparently non-toxic concentration of engineered carbon nanodiamonds (ECNs) is able to induce oxidative/nitrosative stress, imbalance of energy metabolism, and mitochondrial dysfunction in microglial and alveolar basal epithelial cells. Therefore, the complete understanding of their "real" biosafety, along with their possible combination with other molecules mimicking the in vivo milieu, possibly allowing the modulation of their side effects becomes of utmost importance. Based on the above, the focus of the present work was to investigate whether the cellular alterations induced by an apparently non-toxic concentration of ECNs could be counteracted by their incorporation into a synthetic lung surfactant (DPPC:POPG in 7:3 molar ratio). By using two different cell lines (alveolar (A549) and microglial (BV-2)), we were able to show that the presence of lung surfactant decreased the production of ECNs-induced nitric oxide, total reactive oxygen species, and malondialdehyde, as well as counteracted reduced glutathione depletion (A549 cells only), ameliorated cell energy status (ATP and total pool of nicotinic coenzymes), and improved mitochondrial phosphorylating capacity. Overall, our results on alveolar basal epithelial and microglial cell lines clearly depict the benefits coming from the incorporation of carbon nanoparticles into a lung surfactant (mimicking its in vivo lipid composition), creating the basis for the investigation of this combination in vivo.
Asunto(s)
Microglía/efectos de los fármacos , Nanopartículas/toxicidad , Estrés Oxidativo/efectos de los fármacos , Alveolos Pulmonares/efectos de los fármacos , Surfactantes Pulmonares/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Células A549 , Animales , Carbono/química , Muerte Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Glutatión/metabolismo , Humanos , Ratones , Microglía/citología , Microglía/metabolismo , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Nanopartículas/administración & dosificación , Nanopartículas/química , Fosfatidilgliceroles/química , Alveolos Pulmonares/citología , Alveolos Pulmonares/metabolismo , Surfactantes Pulmonares/química , Especies Reactivas de Oxígeno/metabolismo , Pruebas de Toxicidad Subcrónica/métodosRESUMEN
The plasma membranes of archaea are abundant in macrocyclic tetraether lipids that contain a single or double long transmembrane hydrocarbon chains connecting the two glycerol backbones at both ends. In this study, a novel amacrocyclic bisphosphatidylcholine lipid bearing a single membrane-spanning octacosamethylene chain, 1,1'-O-octacosamethylene-2,2'-di-O-tetradecyl-bis-(sn-glycero)-3,3'-diphosphocholine (AC-(di-O-C14PC)2), was synthesized to elucidate effects of the interlayer cross-linkage on membrane properties based on comparison with its corresponding diether phosphatidylcholine, 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (DTPC), that forms bilayer membrane. Several physicochemical techniques demonstrated that while AC-(di-O-C14PC)2 monolayer, which adopts a particularly high-ordered structure in the gel phase, shows remarkably high thermotropic transition temperature compared to DTPC bilayer, the fluidity of both phospholipids above the transition temperature is comparable. Nonetheless, the fluorescent dye leakage from inside the AC-(di-O-C14PC)2 vesicles in the fluid phase is highly suppressed. The origin of the membrane properties characteristic of AC-(di-O-C14PC)2 monolayer is discussed in terms of the single long transmembrane hydrophobic linkage and the diffusional motion of the lipid molecules.
Asunto(s)
Membrana Dobles de Lípidos/química , Fosfatidilcolinas/química , 1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Rastreo Diferencial de Calorimetría , Membrana Dobles de Lípidos/metabolismo , Fluidez de la Membrana , Fosfatidilcolinas/síntesis química , Fosfatidilcolinas/metabolismo , Termodinámica , Temperatura de TransiciónRESUMEN
In this work, we studied the mechanisms of classical activation and inactivation of signal transduction by the histamine H3 receptor, a 7-helix transmembrane bundle G-Protein Coupled Receptor through long-time-scale atomistic molecular dynamics simulations of the receptor embedded in a hydrated double layer of dipalmitoyl phosphatidyl choline, a zwitterionic polysaturated ordered lipid. Three systems were prepared: the apo receptor, representing the constitutively active receptor; and two holo-receptors-the receptor coupled to the antagonist/inverse agonist ciproxifan, representing the inactive state of the receptor, and the receptor coupled to the endogenous agonist histamine and representing the active state of the receptor. An extensive analysis of the simulation showed that the three states of H3R present significant structural and dynamical differences as well as a complex behavior given that the measured properties interact in multiple and interdependent ways. In addition, the simulations described an unexpected escape of histamine from the orthosteric binding site, in agreement with the experimental modest affinities and rapid off-rates of agonists.
Asunto(s)
Simulación de Dinámica Molecular , Receptores Acoplados a Proteínas G/metabolismo , Receptores Histamínicos H3/metabolismo , Transducción de Señal/genética , Transducción de Señal/fisiología , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Animales , Sitios de Unión , Unión Proteica , RatasRESUMEN
Lung lipid metabolism participates both in infant and adult pulmonary disease. The lung is composed by multiple cell types with specialized functions and coordinately acting to meet specific physiologic requirements. The alveoli are the niche of the most active lipid metabolic cell in the lung, the type 2 cell (T2C). T2C synthesize surfactant lipids that are an absolute requirement for respiration, including dipalmitoylphosphatidylcholine. After its synthesis and secretion into the alveoli, surfactant is recycled by the T2C or degraded by the alveolar macrophages (AM). Surfactant biosynthesis and recycling is tightly regulated, and dysregulation of this pathway occurs in many pulmonary disease processes. Alveolar lipids can participate in the development of pulmonary disease from their extracellular location in the lumen of the alveoli, and from their intracellular location in T2C or AM. External insults like smoke and pollution can disturb surfactant homeostasis and result in either surfactant insufficiency or accumulation. But disruption of surfactant homeostasis is also observed in many chronic adult diseases, including chronic obstructive pulmonary disease (COPD), and others. Sustained damage to the T2C is one of the postulated causes of idiopathic pulmonary fibrosis (IPF), and surfactant homeostasis is disrupted during fibrotic conditions. Similarly, surfactant homeostasis is impacted during acute respiratory distress syndrome (ARDS) and infections. Bioactive lipids like eicosanoids and sphingolipids also participate in chronic lung disease and in respiratory infections. We review the most recent knowledge on alveolar lipids and their essential metabolic and signaling functions during homeostasis and during some of the most commonly observed pulmonary diseases.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/metabolismo , Enfermedades Pulmonares/genética , Alveolos Pulmonares/metabolismo , Síndrome de Dificultad Respiratoria/metabolismo , Humanos , Metabolismo de los Lípidos/genética , Pulmón/metabolismo , Pulmón/patología , Enfermedades Pulmonares/metabolismo , Enfermedades Pulmonares/patología , Macrófagos Alveolares/metabolismo , Macrófagos Alveolares/patología , Alveolos Pulmonares/patología , Surfactantes Pulmonares/metabolismo , Síndrome de Dificultad Respiratoria/genética , Síndrome de Dificultad Respiratoria/patologíaRESUMEN
Amyloid-beta (Aß) protein is related to Alzheimer disease (AD), and various experiments have shown that oligomers as small as dimers are cytotoxic. Recent studies have concluded that interactions of Aß with neuronal cell membranes lead to disruption of membrane integrity and toxicity and they play a key role in the development of AD. Molecular dynamics (MD) simulations have been used to investigate Aß in aqueous solution and membranes. We have previously studied monomeric Aß40 embedded in dipalmitoylphosphatidylcholine (DPPC) membrane using MD simulations. Here, we explore interactions of two Aß40 peptides in DPPC bilayer and its consequences on dimer distribution in a lipid bilayer and on the secondary structure of the peptides. We explored that N-terminals played an important role in dimeric Aß peptide aggregations and Aß-bilayer interactions, while C-terminals bound peptides to bilayer like anchors. We did not observe exiting of peptides in our simulations although we observed insertion of peptides into the core of bilayer in some of our simulations. So it seems that the presence of Aß on membrane surface increases its aggregation rate, and as diffusion occurs in two dimensions, it can increase the probability of interpeptide interactions. We found that dimeric Aß, like monomeric one, had the ability to cause structural destabilization of DPPC membrane, which in turn might ultimately lead to cell death in an in vivo system. This information could have important implications for understanding the affinity of Aß oligomers (here dimer) for membranes and the mechanism of Aß oligomer toxicity in AD.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/química , Péptidos beta-Amiloides/química , Membrana Dobles de Lípidos/química , Simulación de Dinámica Molecular , Fragmentos de Péptidos/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Péptidos beta-Amiloides/metabolismo , Sitios de Unión , Humanos , Enlace de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Membrana Dobles de Lípidos/metabolismo , Membranas Artificiales , Fragmentos de Péptidos/metabolismo , Agregado de Proteínas , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , Multimerización de Proteína , Soluciones , Temperatura , TermodinámicaRESUMEN
Melatonin is a neurohormone that has been shown to be protective in Alzheimer's diseases against amyloid-ß (Aß) toxicity, which involves interaction of Aß with neuronal membrane. Non-specific interactions of melatonin with cell membrane may play a physiological role in this process by preserving membrane fluidity. In the brain, melatonin is derived from the amino acid tryptophan through a pathway that includes serotonin and N-acetylserotonin (NAS). How these molecules affect the membrane properties is not understood. In this work, we studied interactions of melatonin and its metabolic precursors tryptophan, serotonin and NAS with dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface using Langmuir monolayer technique. Analysis of compression isotherms, phase transitions and compressibility moduli indicate that all four molecules alter the DPPC monolayer properties in a structure and concentration dependent manner. This effect was most pronounced for melatonin followed by NAS. Melatonin and NAS both decreased the compressibility modulus and shifted the LE/LC phase transition suggesting an increase in the membrane fluidity. Tryptophan and serotonin caused less pronounced effects on the DPPC isotherm. These differences suggest different interaction mechanisms and may be attributed to the interplay between electrostatic and hydrophobic interactions of these molecules with the zwitterionic DPPC headgroups which correlate with water solubility and oil partition coefficients (LogS and LogP) of each the four molecules. The results here demonstrate how the physiochemical properties of indoles can affect lipid membranes which may shed light on the functional significance of these important neurochemicals and the neuroprotective mechanisms of melatonin.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/química , Melatonina/química , Fluidez de la Membrana , Membranas Artificiales , Serotonina/química , Triptófano/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Enfermedad de Alzheimer/metabolismo , Humanos , Melatonina/metabolismo , Serotonina/metabolismo , Triptófano/metabolismoRESUMEN
Phenothiazines are very effective antipsychotic drugs, which also have anticancer and antimicrobial activities. Despite being used in human treatment, the molecular mechanism of the biological actions of these molecules is not yet understood in detail. The role of the interactions between phenothiazines and proteins or lipid membranes has been much discussed. Herein, fourier-transform infrared (FTIR) spectroscopic studies were used to investigate the effect of three phenothiazines: fluphenazine (FPh); chlorpromazine (ChP); and propionylpromazine (PP) on the structures of a positively charged poly-l-lysine (PLL) peptide, a negatively charged dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylglycerol (DPPC/DPPG) membrane, and on the mutual interactions between electrostatically associated PLL molecules and DPPC/DPPG membranes. Phenothiazine-induced alterations in the secondary structure of PLL, the conformational state (trans/gauche) of the hydrocarbon lipid chains, and the hydration of the DPPC/DPPG membrane interface were studied on the basis of amide I' vibrations, antisymmetric and symmetric stretching vibrations of the CH2 groups of the lipid hydrocarbon chains (νsCH2), and stretching vibrations of the lipid C=O groups (νCâ¯=â¯O), respectively. It was shown that in the presence of negatively charged DPPC/DPPG membranes, the phenothiazines were able to modify the secondary structure of charged PLL molecules. Additionally, the effect of PLL on the structure of DPPC/DPPG membranes was also altered by the presence of the phenothiazine molecules.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/metabolismo , Antipsicóticos/farmacología , Clorpromazina/farmacología , Flufenazina/farmacología , Fosfatidilgliceroles/metabolismo , Promazina/análogos & derivados , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Humanos , Polilisina/metabolismo , Promazina/farmacología , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
Controlled shock wave has its application in drug delivery via induced membrane permeability. The magnitude of the impulse force to influence the membrane permeability can be abridged via communion effect of shock wave and external applied electric field of reduced threshold. Controlled shock wave have application at targeting membrane site and are used in drug delivery. Electric field influences the phospholipid bilayer structure by creating transient nanometer-sized pores and has application in targeted chemotherapeutic drug delivery. The synergistic input compensates for increased membrane permeability, reduced threshold magnitude and time for transient poration. The hypothesis is analyzed via Molecular Dynamic (MD) simulation. MARTINI coarse grain force field is used to evaluate the changes in the permeability region of the Dipalmitoyl phosphatidylcholine (DPPC) bilayers during the effect. DPPC has been used in the previous literature to model biological membranes. The hydrophobic DPPC region showed an increased permeability during the synergistic effect via transient nanopores formed due to the perturbation. The study of the time-variant synergistic effect will allow molecular-level understanding of the dynamics of the cell membrane permeability for future drug delivery procedure.
Asunto(s)
Permeabilidad de la Membrana Celular , Electricidad , Ondas de Choque de Alta Energía , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Simulación de Dinámica MolecularRESUMEN
The bidirectional force transmission process of integrin through the cell membrane is still not well understood. Several possible mechanisms have been discussed in literature on the basis of experimental data, and in this study, we investigate these mechanisms by free and steered molecular dynamics simulations. For the first time, constant velocity pulling on the complete integrin molecule inside a dipalmitoyl-phosphatidylcholine membrane is conducted. From the results, the most likely mechanism for inside-out and outside-in signaling is the switchblade model with further separation of the transmembrane helices.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/química , Integrina alfaVbeta3/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Sitios de Unión , Membrana Celular/química , Membrana Celular/metabolismo , Cristalografía por Rayos X , Matriz Extracelular/química , Matriz Extracelular/metabolismo , Humanos , Integrina alfaVbeta3/genética , Integrina alfaVbeta3/metabolismo , Simulación de Dinámica Molecular , Análisis de Componente Principal , Unión Proteica , Conformación Proteica en Hélice alfa , Conformación Proteica en Lámina beta , Dominios y Motivos de Interacción de Proteínas , TermodinámicaRESUMEN
BACKGROUND: After the discovery of membrane-reversible electroporation decades ago, the procedure has been used extensively in biology, biotechnology and medicine. The research on the basic mechanism has increasingly attracted attention. Although most research has focused on models that consider all atomic and molecular interactions and much atomic-level information can be obtained, the huge computational demand limits the models to simulations of only a few nanometers on the spatial scale and a few nanoseconds on the time scale. In order to more comprehensively study the reversible electroporation mechanism of phospholipid membrane on the nanoscale and at longer time intervals of up to 100 ns, we developed a dipalmitoylphosphatidylcholine (DPPC) phospholipid membrane model with the coarse-grained Martini force field. The model was tested by separately examining the morphology of the phospholipid membrane, the hydrophilic channel size, the distribution of the voltage potential on both sides of the membrane, and the movement of water molecules and ions during electroporation. RESULTS: The results showed that the process went through several stages: (1) the formation of the pore with defects originating on the surface. (2) The maintenance of the pore. The defects expanded to large pores and the size remains unchanged for several nanoseconds. (3) Pore healing stage due to self-assembly. Phospholipid membrane shrunk and the pore size decreased until completely closed. The pores were not circular in cross-section for most of the time and the potential difference across the membrane decreased dramatically after the pores formed, with almost no restoration of membrane integrity even when the pores started to close. CONCLUSIONS: The mechanism of the reversible electroporation process on the nanoscale level, including defects, expansion, stability, and pore closing stages on a longer time scale of up to 100 ns was demonstrated more comprehensively with the coarse-grained Martini force field, which took both the necessary molecular information and the calculation efficiency into account.
Asunto(s)
Membrana Celular/metabolismo , Electroporación , Simulación de Dinámica Molecular , 1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Membrana Celular/química , Interacciones Hidrofóbicas e Hidrofílicas , Membrana Dobles de Lípidos/química , Membrana Dobles de Lípidos/metabolismo , Conformación Molecular , Movimiento , Agua/metabolismoRESUMEN
Matrix vesicles (MVs) are a special class of extracellular vesicles that drive bone and dentin mineralization by providing the essential enzymes and ions for the nucleation and propagation of mineral crystals. Tissue-nonspecific alkaline phosphatase (TNAP) is an integral protein of MV membrane and participates in biomineralization by hydrolyzing extracellular pyrophosphate (PPi), a strong mineralization inhibitor, and forming inorganic phosphate (Pi), necessary for the growth of mineral crystals inside MVs and their propagation once released in the extracellular matrix. MV membrane is enriched in cholesterol (CHOL), which influences the incorporation and activity of integral proteins in biologic membranes; however, how CHOL controls the incorporation and activity of TNAP in MV membrane has not yet been elucidated. In the present study, Langmuir monolayers were used as a MV membrane biomimetic model to assess how CHOL affects TNAP incorporation and activity. Surface pressure-area (π-A) isotherms of binary dipalmitoilphosphatidylcholine (DPPC)/CHOL monolayers showed that TNAP incorporation increases with CHOL concentration. Infrared spectroscopy showed that CHOL influences the conformation and orientation of the enzyme. Optical-fluorescence micrographs of the monolayers revealed the tendency of TNAP to incorporate into CHOL-rich microdomains. These data suggest that TNAP penetrates more efficiently and occupies a higher surface area into monolayers with a lower CHOL concentration due to the higher membrane fluidity. However, the quantity of enzyme transferred to solid supports as well as the enzymatic activity were higher using monolayers with a higher CHOL concentration due to increased rigidity that changes the enzyme orientation at the air-solid interface. These data provide new insights regarding the interfacial behavior of TNAP and CHOL in MVs and shed light on the biochemical and biophysical processes occurring in the MV membrane during biomineralization at the molecular level.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/metabolismo , Fosfatasa Alcalina/metabolismo , Colesterol/metabolismo , Membranas Artificiales , 1,2-Dipalmitoilfosfatidilcolina/química , Fosfatasa Alcalina/química , Catálisis , Colesterol/química , Unión ProteicaRESUMEN
Cultured human lung epithelial cells, particularly A549â¯cells, are commonly used as the in vitro model to evaluate the inhalational toxicity of nanoparticles (NPs). However, A549â¯cells are cancer cells that might not reflect the response of normal tissues to NP exposure. In addition, the possible influence of pulmonary surfactant also should be considered. This study used silica NPs as model NPs, and evaluated the toxicity of silica NPs to both 16HBE human bronchial epithelial cells and A549 adenocarcinomic cells, with or without the presence of pulmonary surfactant component dipalmitoyl phosphatidylcholine (DPPC). We found that silica NPs induced cytotoxicity at the concentration of 128⯵g/mL in 16HBE cells but not A5490â¯cells, and the cytotoxicity of silica NPs to 16HBE cells was inhibited by DPPC. Intracellular reactive oxygen species (ROS) was only induced in 16HBE cells, accompanying with decreased thiol levels. Moreover, 16HBE cells internalized more silica NPs compared with A549â¯cells, and the internalization was reduced with the presence of DPPC in both types of cells. The retention of ABC transporter substrate Calcein was only significantly induced by silica NPs at high concentrations in 16HBE cells, and was partially reduced due to the presence of DPPC. In addition, ABC transporter inhibitor MK571 increased the toxicity of silica NPs to both types of cells, with 16HBE cells being more sensitive. Our data revealed that the cell types and pulmonary surfactant components could influence the toxicological consequences of silica NPs to human lung cells. Therefore, it is recommended that in vitro studies should carefully select suitable models to evaluate the inhalational toxicity of NPs.
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1,2-Dipalmitoilfosfatidilcolina/metabolismo , Células Epiteliales/efectos de los fármacos , Pulmón/efectos de los fármacos , Nanopartículas/toxicidad , Surfactantes Pulmonares/metabolismo , Dióxido de Silicio/toxicidad , 1,2-Dipalmitoilfosfatidilcolina/análogos & derivados , Células A549 , Supervivencia Celular/efectos de los fármacos , Células Epiteliales/metabolismo , Humanos , Pulmón/metabolismo , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Two 15 µs all-atom simulations of the A2A adenosine receptor were obtained in a ternary mixture of cholesterol, saturated phosphatidylcholine lipids, and unsaturated phosphatidylcholine lipids. An analysis of local lipid solvation is reported on the basis of a Voronoi tessellation of the upper and lower leaflets, identifying first and second solvation shells. The local environments of both the inactive state and the partially active state of the receptor are significantly enriched with unsaturated chains but depleted of cholesterol and saturated chains, relative to the bulk membrane composition. In spite of the local depletion of cholesterol, the partially active receptor binds cholesterol at three locations during the entire simulation trajectory. These long-lived interactions represent the extreme of a very broad distribution of first-solvation shell lipid lifetimes, confounding sharp distinctions between lipid interactions. The broad distributions of lifetimes also make equilibrating the local lipid environment difficult, necessitating long simulation times.
Asunto(s)
1,2-Dipalmitoilfosfatidilcolina/metabolismo , Colesterol/metabolismo , Membrana Dobles de Lípidos/metabolismo , Fosfatidilcolinas/metabolismo , Receptor de Adenosina A2A/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/química , Sitios de Unión , Colesterol/química , Enlace de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Membrana Dobles de Lípidos/química , Simulación de Dinámica Molecular , Fosfatidilcolinas/química , Estructura Secundaria de Proteína , Receptor de Adenosina A2A/químicaRESUMEN
Cu(i) binds to the N-terminal metal binding domain (MBD) of hCTR1 and induces its conformational change, which promotes the interaction of the MBD with cell membranes. The membrane interaction was confirmed in living cells. This process could be the first step to initiate the cellular uptake of copper ions by hCTR1.