RESUMO
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.
Assuntos
Dimiristoilfosfatidilcolina , Fenilalanina , Fenilalanina/química , Fenilalanina/metabolismo , Dimiristoilfosfatidilcolina/química , Espectroscopia de Infravermelho com Transformada de Fourier , Bicamadas Lipídicas/química , Bicamadas Lipídicas/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Lipídeos de Membrana/química , Lipídeos de Membrana/metabolismoRESUMO
This study analyses the insertion of Chlorogenic acid (CGA) in phosphatidylcholine (PC) membranes enriched with cholesterol (Chol). While cholesterol decreases the area per lipid and increases the dipole potential, CGA increases and decreases these values, respectively. When CGA is inserted into cholesterol-containing DMPC membranes, these effects cancel out, resulting in values that overlap with those of DMPC monolayers without Chol and CGA. The presence of CGA also compensates the increase of dipole potential produced by Chol which can be explain as a consequence of the orientation of CGA molecule at the interphase opposing the cholesterol dipole moieties and water dipoles. This compensatory effect is less effective when lipids lack carbonyl groups (CO). When monolayers are composed by unsaturated PCs the Chol compensation is found at higher concentrations of CGA due to the direct interaction between CGA and Chol. These results suggest that cholesterol modulates the interaction and distribution of CGA in the lipid membrane, which may have implications for its biological activity.
Assuntos
Dimiristoilfosfatidilcolina , Fosfatidilcolinas , Ácido Clorogênico , Colesterol , Bicamadas Lipídicas , Propriedades de SuperfícieRESUMO
Calcium ion regulation plays a crucial role in maintaining neuronal functions such as neurotransmitter release and synaptic plasticity. Copper (Cu2+ ) coordination to amyloid-ß (Aß) has accelerated Aß1-42 aggregation that can trigger calcium dysregulation by enhancing the influx of calcium ions by extensive perturbing integrity of the membranes. Aß1-42 aggregation, calcium dysregulation, and membrane damage are Alzheimer disease (AD) implications. To gain a detail of calcium ions' role in the full-length Aß1-42 and Aß1-42 -Cu2+ monomers contact, the cellular membrane before their aggregation to elucidate the neurotoxicity mechanism, we carried out 2.5 µs extensive molecular dynamics simulation (MD) to rigorous explorations of the intriguing feature of the Aß1-42 and Aß1-42 -Cu2+ interaction with the dimyristoylphosphatidylcholine (DMPC) bilayer in the presence of calcium ions. The outcome of the results compared to the same simulations without calcium ions. We surprisingly noted robust binding energies between the Aß1-42 and membrane observed in simulations containing without calcium ions and is two and a half fold lesser in the simulation with calcium ions. Therefore, in the case of the absence of calcium ions, N-terminal residues of Aß1-42 deeply penetrate from the surface to the center of the bilayer; in contrast to calcium ions presence, the N- and C-terminal residues are involved only in surface contacts through binding phosphate moieties. On the other hand, Aß1-42 -Cu2+ actively participated in surface bilayer contacts in the absence of calcium ions. These contacts are prevented by forming a calcium bridge between Aß1-42 -Cu2+ and the DMPC bilayer in the case of calcium ions presence. In a nutshell, Calcium ions do not allow Aß1-42 penetration into the membranes nor contact of Aß1-42 -Cu2+ with the membranes. These pieces of information imply that the calcium ions mediate the membrane perturbation via the monomer interactions but do not damage the membrane; they agree with the western blot experimental results of a higher concentration of calcium ions inhibit the membrane pore formation by Aß peptides.
Assuntos
Doença de Alzheimer , Humanos , Doença de Alzheimer/metabolismo , Cálcio , Dimiristoilfosfatidilcolina , Fragmentos de Peptídeos/química , Peptídeos beta-Amiloides/química , Cobre/química , ÍonsRESUMO
Pluronic/lipid mix promises stealth liposomes with long circulation time and long-term stability for pharmaceutical applications. However, the influence of Pluronics on several aspects of lipid membranes has not been fully elucidated. Herein it was described the effect of Pluronics on the structured water, alkyl chain conformation, and kinetic stability of dimyristoylphosphatidylcholine (DMPC) liposomes using interfacial and deeper fluorescent probes along with computational molecular modeling data. Interfacial water changed as a function of Pluronics' hydrophobicity with polypropylene oxide (PPO) anchoring the copolymers in the lipid bilayer. Pluronics with more than 30-40 PO units had facilitated penetration at the bilayer while shorter PPO favored a more interfacial interaction. Low Pluronic concentrations provided long-term stability of vesicles by steric effects of polyethylene oxide (PEO), but high amounts destabilized the vesicles as a sum of water-bridge cleavage at the polar head group and the reduced alkyl-alkyl interactions among the lipids. The high kinetic stability of Pluronic/DMPC vesicles is a proof-of-concept of its advantages and applicability in nanotechnology over conventional liposome-based pharmaceutical products for future biomedical applications.
Assuntos
Dimiristoilfosfatidilcolina , Poloxâmero , Bicamadas Lipídicas , Lipossomos , Polietilenoglicóis , ÁguaRESUMO
Cells are dynamic systems with complex mechanical properties, regulated by the presence of different species of proteins capable to assemble (and disassemble) into filamentous forms as required by different cells functions. Giant unilamellar vesicles (GUVs) of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) are systems frequently used as a simplified model of cells because they offer the possibility of assaying separately different stimuli, which is no possible in living cells. Here we present a study of the effect of acting protein on mechanical properties of GUVs, when the protein is inside the vesicles in either monomeric G-actin or filamentous F-actin. For this, rabbit skeletal muscle G-actin is introduced inside GUVs by the electroformation method. Protein polymerization inside the GUVs is promoted by adding to the solution MgCl2 and the ion carrier A23187 to allow the transport of Mg+2 ions into the GUVs. To determine how the presence of actin changes the mechanical properties of GUVs, the vesicles are deformed by the application of an AC electric field in both cases with G-actin and with polymerized F-actin. The changes in shape of the vesicles are characterized by optical microscopy and from them the bending stiffness of the membrane are determined. It is found that G-actin has no appreciable effect on the bending stiffness of DMPC GUVs, but the polymerized actin makes the vesicles more rigid and therefore more resistant to deformations. This result is supported by evidence that actin filaments tend to accumulate near the membrane.
Assuntos
Actinas/química , Dimiristoilfosfatidilcolina/química , Eletricidade , Lipossomas Unilamelares/química , Citoesqueleto de Actina/química , Actinas/metabolismo , Animais , Calcimicina/química , Cloreto de Magnésio/química , Cloreto de Magnésio/metabolismo , Microscopia , Músculo Esquelético/metabolismo , Coelhos , Tensão Superficial , Lipossomas Unilamelares/metabolismo , ViscosidadeRESUMO
N-(2-Hydroxyphenyl)-2-propylpentanamide (HO-AAVPA) is a valproic acid (VPA) derivative that has shown promising antiproliferative effects in different cancer cell lines, such as A204, HeLa, and MDA-MB-231. However, its low water solubility could reduce its therapeutic effectiveness. To solve this problem, in this work, we incorporated HO-AAVPA into dimyristoyl-phosphatidylcholine (DMPC) liposomes in the presence or absence of cholesterol (CHOL). Using differential scanning calorimetry (DSC), we found that the transition enthalpy (ΔHtr) of DMPC liposomes is reduced in the presence of CHOL and/or HO-AAVPA, indicating the favorable interactions between CHOL and/or HO-AAVPA and DMPC. Further, by molecular dynamics simulations it was possible to observed that HO-AAVPA migrates from the center of the bilayer toward the water and lipid interface of the DPMC bilayer systems exposing the amine group to water and the aliphatic chain toward the interior of the bilayer. As a consequence, we observed an ordering of the lipid bilayer. Moreover, CHOL harbors into the inner bilayer membrane, increasing the order parameter of the system. The liposomal solutions loaded with HO-AAVPA were tested in the NIH3T3 cell line, showing a reduction in cell proliferation compared to those cells presented without liposomes.Communicated by Ramaswamy H. Sarma.
Assuntos
Dimiristoilfosfatidilcolina , Lipossomos , Camundongos , Animais , Dimiristoilfosfatidilcolina/química , Dimiristoilfosfatidilcolina/metabolismo , Lipossomos/química , Células NIH 3T3 , Bicamadas Lipídicas/química , Colesterol/química , ÁguaRESUMO
The insertion process of Naproxen into model dimyristoylphosphatidylcholine (DMPC) membranes is studied by resorting to state-of-the-art classical and quantum mechanical atomistic computational approaches. Molecular dynamics simulations indicate that anionic Naproxen finds an equilibrium position right at the polar/nonpolar interphase when the process takes place in aqueous environments. With respect to the reference aqueous phase, the insertion process faces a small energy barrier of ≈5 kJ mol-1 and yields a net stabilization of also ≈5 kJ mol-1. Entropy changes along the insertion path, mainly due to a growing number of realizable microstates because of structural reorganization, are the main factors driving the insertion. An attractive fluxional wall of noncovalent interactions is characterized by all-quantum descriptors of chemical bonding (natural bond orbitals, quantum theory of atoms in molecules, noncovalent interaction, density differences, and natural charges). This attractive wall originates in the accumulation of tiny transfers of electron densities to the interstitial region between the fragments from a multitude of individual intermolecular contacts stabilizing the tertiary drug/water/membrane system.
Assuntos
Dimiristoilfosfatidilcolina , Naproxeno , Membrana Celular , Simulação de Dinâmica Molecular , TermodinâmicaRESUMO
Epirubicin is a cytotoxic drug used in the treatment of different types of cancer and increasing evidence suggests that its target is cell membranes. In order to gain insight on its toxic effects, intact red blood cells (RBC), human erythrocyte membranes and molecular models were used. The latter consisted in bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), phospholipid classes found mainly in the outer and inner monolayers of the human erythrocyte membrane, respectively. The results obtained by X-ray diffraction displayed that epirubicin induced structural perturbations in multilayers of DMPC. Differential scanning calorimetry (DSC) showed that epirubicin disturbed the thermotropic behavior of both DMPC and DMPE vesicles, whereas fluorescence spectroscopy demonstrated alterations in the fluidity of DMPC vesicles and the erythrocyte membrane. Scanning electron microscopy (SEM) revealed that epirubicin changed the normal discoid form of RBC to echinocytes and stomatocytes. Electron paramagnetic resonance (EPR) disclosed that this drug induced conformational changes in the erythrocyte membrane proteins. These findings demonstrate that epirubicin interacts with lipids and proteins of the human erythrocyte membrane, effects that might compromise the integrity and function of cell membranes. This is the first time that its toxic effects on the human erythrocyte membrane have been described.
Assuntos
Antibióticos Antineoplásicos/toxicidade , Epirubicina/toxicidade , Eritrócitos/efeitos dos fármacos , Varredura Diferencial de Calorimetria , Células Cultivadas , Dimiristoilfosfatidilcolina , Eritrócitos/patologia , Eritrócitos/ultraestrutura , Humanos , Lipossomos , Microscopia Eletrônica de Varredura , Fosfatidiletanolaminas , Difração de Raios XRESUMO
Bone biomineralization is mediated by a special class of extracellular vesicles, named matrix vesicles (MVs), released by osteogenic cells. The MV membrane is enriched in sphingomyelin (SM), cholesterol (Chol) and tissue non-specific alkaline phosphatase (TNAP) compared with the parent cells' plasma membrane. TNAP is an ATP phosphohydrolase bound to cell and MV membranes via a glycosylphosphatidylinositol (GPI) anchor. Previous studies have shown that the lipid microenvironment influences the catalytic activity of enzymes incorporated into lipid bilayers. However, there is a lack of information about how the lipid microenvironment controls the ability of MV membrane-bound enzymes to induce mineral precipitation. Herein, we used TNAP-harboring proteoliposomes made of either pure dimyristoylphosphatidylcholine (DMPC) or DMPC mixed with either Chol, SM or both of them as MV biomimetic systems to evaluate how the composition modulates the lipid microenvironment and, in turn, TNAP incorporation into the lipid bilayer by means of calorimetry. These results were correlated with the proteoliposomes' catalytic activity and ability to induce the precipitation of amorphous calcium phosphate (ACP) in vitro. DMPC:SM proteoliposomes displayed the highest efficiency of mineral propagation, apparent affinity for ATP and substrate hydrolysis efficiency, which correlated with their highest degree of membrane organization (highest ΔH), among the tested proteoliposomes. Results obtained from turbidimetry and Fourier transformed infrared (FTIR) spectroscopy showed that the tested proteoliposomes induced ACP precipitation with the order DMPC:SM>DMPC:Chol:SM≈DMPC:Chol>DMPC which correlated with the lipid organization and the presence of SM in the proteoliposome membrane. Our study arises important insights regarding the physical properties and role of lipid organization in MV-mediated mineralization.
Assuntos
Trifosfato de Adenosina/metabolismo , Fosfatase Alcalina/metabolismo , Biomineralização/fisiologia , Fosfatos de Cálcio/metabolismo , Lipossomos/metabolismo , Proteolipídeos/metabolismo , Animais , Bovinos , Colesterol/química , Dimiristoilfosfatidilcolina/química , Hidrólise , Lipossomos/química , Proteolipídeos/química , Ratos , Esfingomielinas/químicaRESUMO
Despite decades of intense research to understand the phenomenon of anesthesia and its membrane-related changes in neural transmission, where lipids and proteins have been proposed as primary targets of anesthetics, the involved action mechanisms remain unclear. Based on the overall agreement that anesthetics and neurotransmitters induce particular modifications in the plasma membrane of neurons, triggering specific responses and changes in their energetic states, we present here a thermal study to investigate membrane effects in a lipid-protein model made of 1,2-dimyristoyl-sn-glycero-3-phosphocholine and albumin from chicken egg white under the influence of neurotransmitters and anesthetics. First, we observe how ovalbumin, ovotransferrin, and lysozyme (main albumin constituents from chicken egg white) interact with the lipid membrane enhancing their lipophilic character while exposing their hydrophobic domains. This produces a lipid separation and a more ordered hybrid lipid-protein assembly. Second, we measured the thermotropic changes of this assembly induced by acetylcholine, γ-aminobutiric acid, tetracaine, and pentobarbital. Although the protein in our study is not a receptor, our results are striking, for they give evidence of the great importance of non-specific interactions in the anesthesia mechanism.
Assuntos
Anestésicos/farmacologia , Membranas Artificiais , Modelos Biológicos , Neurotransmissores/farmacologia , Temperatura , Albuminas , Animais , Galinhas , Dimiristoilfosfatidilcolina , Proteínas do Ovo , Interações Hidrofóbicas e Hidrofílicas , Lipídeos de Membrana , Proteínas de MembranaRESUMO
Descriptors of chemical bonding derived from five different analysis tools based on quantum mechanics (natural charges, electron density differences, atoms in molecules (AIM), natural bond orbitals (NBO), and non-covalent interactions (NCI) index) consistently afford a picture of a wall of weak, non-covalent intermolecular interactions separating anionic Ibuprofen from the environment. This wall, arising from the cumulative effect of a multitude of individual weak charge transfer interactions to the interstitial region between fragments, stabilizes the drug at all equilibrium positions in the free energy profile for its insertion into model cell membranes. The formal charge in anionic Ibuprofen strengthens all intermolecular interactions, having a particularly strong effect in the network of water to water hydrogen bonds in the solvent. Electron redistribution during the insertion process leads to a sensible reduction of electron delocalization in both the -CO2- group and the aromatic ring of Ibuprofen. Here, we conclusively show that, despite their purely classical origin, randomly chosen configurations from molecular dynamics simulations provide deep insight into the purely quantum nature of bonding interactions.
Assuntos
Ibuprofeno/química , Bicamadas Lipídicas/química , Ânions/química , Dimiristoilfosfatidilcolina/química , Evolução Molecular , Ligação de Hidrogênio , Ibuprofeno/metabolismo , Bicamadas Lipídicas/metabolismo , Conformação Molecular , Simulação de Dinâmica Molecular , Teoria Quântica , Termodinâmica , Água/químicaRESUMO
Donepezil is used to treat symptomatically the Alzheimer's disease (AD). This drug is a specific inhibitor of the enzyme acetylcholinesterase (AChE), whose main physiological function is to hydrolyze the neurotransmitter acetylcholine. The main objective of this work was to study the effect of donepezil on human erythrocytes as AChE is present in its membrane. For this purpose, human erythrocytes and molecular model of its membrane built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. The latter correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. Our experimental evidences obtained from X-ray diffraction and differential scanning calorimetry (DSC) analysis indicated that donepezil was capable of interacting with both phospholipids. Fluorescence spectroscopy results showed a moderate increase in the fluidity of the hydrophobic tails of DMPC and isolated unsealed human erythrocyte membranes (IUM). On the other hand, results by scanning electron microscopy (SEM) and optical defocusing microscopy (DM) showed that the drug changed the normal biconcave shape of the erythrocytes inducing the formation of stomatocytes (cup-shaped cells). This effect was explained by the incorporation of donepezil molecules into the erythrocyte membrane and interactions with AChE.
Assuntos
Acetilcolinesterase/efeitos dos fármacos , Doença de Alzheimer/tratamento farmacológico , Inibidores da Colinesterase/farmacologia , Donepezila/farmacologia , Eritrócitos/efeitos dos fármacos , Nootrópicos/farmacologia , Inibidores da Colinesterase/uso terapêutico , Dimiristoilfosfatidilcolina/metabolismo , Donepezila/uso terapêutico , Membrana Eritrocítica/efeitos dos fármacos , Membrana Eritrocítica/metabolismo , Humanos , Nootrópicos/uso terapêutico , Fosfatidiletanolaminas/metabolismoRESUMO
OBJECTIVES: Uridine was conjugated with fatty acids to improve the drug lipophilicity and the interaction with phospholipid bilayers. METHODS: The esterification reaction using carbodiimides compounds as coupling agents and a nucleophilic catalyst allowed us to synthesize tri-acyl ester derivatives of uridine with fatty acids. Analysis of molecular interactions between these tri-acyl ester derivatives and l-α-dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles (MLV) - as a mammalian cell membrane model - have been performed by differential scanning calorimetry (DSC). KEY FINDINGS: The DSC thermograms suggest that nucleoside and uridine triacetate softly interact with phospholipidic multilamellar vesicles which are predominantly located between the polar phase, whereas the tri-acyl ester derivatives with fatty acids (myristic and stearic acids) present a strongly interaction with the DMPC bilayer due to the nucleoside and aliphatic chains parts which are oriented towards the polar and lipophilic phases of the phospholipidic bilayer, respectively. However, the effects caused by the tri-myristoyl uridine and tri-stearoyl uridine are different. CONCLUSIONS: We show how the structural changes of uridine modulate the calorimetric behaviour of DMPC shedding light on their affinity with the phospholipidic biomembrane model.
Assuntos
Acetatos/química , Dimiristoilfosfatidilcolina/química , Ésteres/química , Membranas/química , Nucleosídeos/química , Uridina/análogos & derivados , Varredura Diferencial de Calorimetria/métodos , Ácidos Graxos/química , Modelos Teóricos , Fosfolipídeos/química , Uridina/químicaRESUMO
The interactions and the protective effect of epigallocatechin gallate (EGCG) on human erythrocytes (RBC) and molecular models of its membrane were investigated. The latter consisted of bilayers built- up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry experiments showed that EGCG induced significant structural and thermotropic perturbations in multilayers and vesicles of DMPC; however, these effects were not observed in DMPE. Fluorescence spectroscopy results revealed that EGCG produced alterations of the molecular dynamics at the level of the hydrophobic-hydrophilic interface in DMPC vesicles, and in isolated unsealed human erythrocyte membranes (IUM). EGCG also induced morphological alterations in RBC from their normal discoid form to echinocytes. These outcomes indicate that EGCG molecules were located in the outer monolayer of the erythrocyte membrane. The assessment of EGCG protective effect demonstrated that it inhibits the morphological alterations and lysis induced by HClO to human erythrocytes. The results obtained from this study suggest that the insertion of EGCG into the outer monolayer of the erythrocyte membrane might prevent the access and deleterious effects of oxidant molecules such as HClO and free radicals into the red cells, protecting them from oxidative damage.
Assuntos
Antioxidantes/farmacologia , Catequina/análogos & derivados , Membrana Eritrocítica/efeitos dos fármacos , Ácido Hipocloroso/antagonistas & inibidores , Oxidantes/antagonistas & inibidores , Antioxidantes/química , Catequina/química , Catequina/farmacologia , Dimiristoilfosfatidilcolina/química , Membrana Eritrocítica/química , Hemólise/efeitos dos fármacos , Humanos , Interações Hidrofóbicas e Hidrofílicas , Ácido Hipocloroso/farmacologia , Cinética , Bicamadas Lipídicas/química , Oxidantes/farmacologia , Fosfatidiletanolaminas/química , Espectrometria de Fluorescência , TermodinâmicaRESUMO
This study was aimed at elucidating the molecular mechanisms of the interaction of the antitumor alkylphospholipid drug miltefosine with human erythrocytes (RBC) and molecular models of its membrane. The latter consisted of bilayers of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray results showed that the drug interacted with DMPC multilayers; however, no effects on DMPE were detected. The experimental findings obtained by differential scanning calorimetry (DSC) indicated that miltefosine altered the thermotropic behavior of both DMPC and DMPE vesicles. Fluorescence spectroscopy evidenced an increase in the fluidity of DMPC vesicles and human erythrocyte membranes. Scanning electron microscopy (SEM) observations on human erythrocytes showed that miltefosine induced morphological alterations to RBC from its normal biconcave to an echinocyte type of shape. These results confirm that miltefosine interacts with the outer moiety of the human erythrocyte membrane affecting the cell morphology.
Assuntos
Antineoplásicos/farmacologia , Membrana Eritrocítica/efeitos dos fármacos , Eritrócitos/efeitos dos fármacos , Bicamadas Lipídicas/química , Fosfolipídeos/química , Fosforilcolina/análogos & derivados , Varredura Diferencial de Calorimetria , Dimiristoilfosfatidilcolina/química , Eritrócitos/citologia , Hemólise , Humanos , Microscopia Eletrônica de Varredura , Modelos Moleculares , Fosfatidiletanolaminas/química , Fosforilcolina/farmacologia , Espectrometria de Fluorescência , Termodinâmica , Difração de Raios XRESUMO
The interaction and protective effect of caffeic acid (CA) on human erythrocytes (RBC) and molecular models of its membrane were studied. The latter consisted of bilayers built up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), representative of phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry results indicated that CA induced structural and thermotropic perturbations in multilayers and vesicles of DMPC. Fluorescence spectroscopy analysis showed that CA increased the fluidity of DMPC vesicles and of human erythrocyte ghosts. Scanning electron microscopy observations displayed that CA induced morphological alterations to RBC from their normal discoid form to echinocytes. The assessment of its protective capacity showed that CA inhibits RBC morphological alterations and lysis induced by HClO. These findings imply that CA molecules were located in the outer monolayer of the erythrocyte membrane, and that this preferential location might effectively protect the red cells from damage caused by oxidizing species.
Assuntos
Ácidos Cafeicos/farmacologia , Eritrócitos/efeitos dos fármacos , Varredura Diferencial de Calorimetria , Dimiristoilfosfatidilcolina/metabolismo , Eritrócitos/metabolismo , Glicerofosfolipídeos/metabolismo , Hemólise/efeitos dos fármacos , Humanos , Técnicas In Vitro , Microscopia Eletrônica de Varredura , Espectrometria de Fluorescência , Difração de Raios XRESUMO
Labetalol is one of the most used drugs for the treatment of hypertension. This molecule is able to bind to both alpha-1 (α1) and beta (ß) adrenergic receptors present in vascular smooth muscle among other tissues. It has been determined that human erythrocytes possess both alpha receptors and beta-adrenergic receptors expressed on their surface. The objective of this work was to study the effect of labetalol on the morphology of human erythrocytes. To accomplish this goal, human erythrocytes and model membranes built of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. These lipid species are present in the outer and inner monolayers of the red blood cell membrane, respectively. Our findings obtained by X-ray diffraction and differential scanning calorimetry (DSC) indicate that labetalol interacted with both lipids in a process dependent on concentration. In fact, at low concentrations labetalol preferentially interacted with DMPE. On the other hand, results obtained by scanning electron microscopy (SEM) showed that labetalol alters the normal biconcave form of erythrocytes to stomatocytes and knizocytes (cells with one or more cavities, respectively). According to the bilayers couple hypothesis, this result implied that the drug inserted in the inner monolayer of the human erythrocyte membrane.
Assuntos
Antagonistas de Receptores Adrenérgicos alfa 1/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Eritrócitos/efeitos dos fármacos , Labetalol/farmacologia , Antagonistas de Receptores Adrenérgicos alfa 1/química , Antagonistas Adrenérgicos beta/química , Varredura Diferencial de Calorimetria , Dimiristoilfosfatidilcolina/química , Membrana Eritrocítica/efeitos dos fármacos , Membrana Eritrocítica/metabolismo , Membrana Eritrocítica/ultraestrutura , Eritrócitos/metabolismo , Eritrócitos/ultraestrutura , Humanos , Técnicas In Vitro , Labetalol/química , Lipossomos/química , Membranas Artificiais , Microscopia Eletrônica de Varredura , Fosfatidiletanolaminas/química , Difração de Raios XRESUMO
Differential scanning calorimetry (DSC) is a thermoanalytical technique which provides information on the interaction between drugs and models of cell membranes. Studies on the calorimetric behavior of hydrated phospholipids within liposomes are employed to shed light on the changes in the physico-chemical properties when interacting with drugs. In this report, new potential anti-cancer drugs such as uridine and uridine derivatives (acetonide and its succinate), 3ß-5α,8α-endoperoxide-cholestan-6-en-3-ol (5,8-epidioxicholesterol) and conjugate (uridine acetonide-epidioxicholesterol succinate) have been synthesized. Steglich esterification method using coupling agents allowed to obtain the uridine acetonide-sterol conjugate. The study on the interaction between the drugs and dimiristoyl-phophatidilcholine (DMPC) liposomes has been conducted by the use of DSC. The analysis of the DSC curves indicated that the uridine and derivatives (acetonide and its succinate) present a very soft interaction with the DMPC liposomes, whereas the 5,8-epidioxicholesterol and the conjugate showed a strong effect on the thermotropic behavior. Our results suggested that the lipophilic character of uridine acetonide-sterol conjugate improves the affinity with the DMPC liposomes.
Assuntos
Varredura Diferencial de Calorimetria/métodos , Dimiristoilfosfatidilcolina/química , Lipossomos/química , Pró-Fármacos/química , Esteróis/química , Uridina/químicaRESUMO
Coarse-grained simulation schemes are increasingly gaining popularity in the scientific community because of the significant speed up granted, allowing a considerable expansion of the accessible time and size scales accessible to molecular simulations. However, the number of compatible force fields capable of representing ensembles containing different molecular species (i.e., Protein, DNA, etc) is still limited. Here, we present a set of parameters and simplified representation for lipids compatible with the SIRAH force field for coarse-grained simulations ( http://www.sirahff.com ). We show that the present model not only achieves a correct reproduction of structural parameters as area per lipid and thickness, but also dynamic descriptors such as diffusion coefficient, order parameters, and proper temperature driven variations. Adding phospholipid membranes to the existing aqueous solution, protein and DNA representations of the SIRAH force field permit considering the most common problems tackled by the biomolecular simulation community.
Assuntos
Dimiristoilfosfatidilcolina , Bicamadas Lipídicas/química , Simulação de Dinâmica Molecular , DNA/química , Proteínas/químicaRESUMO
We study the molecular dynamics of lipids in binary large unilamellar liposomes suspended in D2O composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or soy phosphatidylcholine (SPC) additivated with different percentiles of sodium deoxycholate (SDC). We use the fast field-cycling proton NMR relaxometry technique over a wide timescale and at diverse temperatures. A model previously validated in different formulations is here employed for the relaxometric analysis of elastic vesicles. A new dynamical regime is observed for the first time in additivated DMPC and additivated/non-additivated SPC liposomes. This surprising feature is discussed in terms of vesicle shape fluctuations, enhanced elasticity and lipid & additive diffusion within the membrane. The continuum elastic theory is revisited for a better understanding of recent experiments and those here presented. We address the point of deformability measurements across rigid permeable barriers versus measurements of the bending elastic modulus in free-standing vesicles.