Terbutaline sulphate (TS) is a selective short-acting β2 adrenoceptor agonist used for asthma treatment. The pharmacological activity of TS depends on its binding to the transmembrane protein, β2 adrenoceptor. Thus, the interactions of this drug with biological membranes are expected, affecting its pharmacological activity. Using in vitro models to study the interaction of TS with biological membranes can provide important information about the activity of the drug. Here, liposomes with different lipid compositions were used as biomimetic models of cell membranes to evaluate the effect of composition, complexity, and physical state of membranes on TS-membrane interactions. For that, liposomes containing dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and liposomes containing DMPC and cholesterol (CHOL) were prepared. For the study of TS-membrane interactions, the TS lipophilicity was evaluated in terms of i) partition coefficient; ii) the preferential location of the drug within the membrane; iii) and the effect of TS on the membrane fluidity. The obtained data suggest that TS has an affinity for the lipid membrane, partitioning from the aqueous to the lipid phase. The affinity was dependent on the liposomes\' compositions, showing a greater affinity for DMPC membranes than for DMPC:CHOL model. Dynamic light scattering (DLS) results revealed that this is due to the rigidizing effect caused by CHOL molecules. These findings provide valuable insights in the understanding of the complex interaction of TS with biomembrane models as well as the relevance of lipid compositions and membrane structure in such interactions, which may be related to its pharmacological activity and side effects.

Lipids play a central role in many infectious diseases. AIDS (Acquired Immune Deficiency Syndrome) and tuberculosis are two of the deadliest infectious diseases to have struck mankind. The pathogens responsible for these diseases, Human Immunodeficiency Virus-1 and Mycobacterium tuberculosis, rely on lipids and on lipid membrane properties to gain access to their host cells, to persist in them and ultimately to egress from their hosts. In this Review, we discuss the life cycles of these pathogens and the roles played by lipids and membranes. We then give an overview of therapies that target lipid metabolism, modulate host membrane properties or implement lipid-based drug delivery systems. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Several lipid classes constitute the universal matrix of the biological membranes. With their amphipathic nature, lipids not only build the continuous barrier that confers identity to every cell and organelle, but they are also active actors that modulate the activity of the proteins immersed in the lipid bilayer. The plasma membrane H(+)-ATPase, an enzyme from plant cells, is an excellent example of a transmembrane protein whose activity is influenced by the hydrophilic compartments at both sides of the membrane and by the hydrophobic domains of the lipid bilayer. As a result, an extensive documentation of the effect of numerous amphiphiles in the enzyme activity can be found. Detergents, membrane glycerolipids, and sterols can produce activation or inhibition of the enzyme activity. In some cases, these effects are associated with the lipids of the membrane bulk, but in others, a direct interaction of the lipid with the protein is involved. This review gives an account of reports related to the action of the membrane lipids on the H(+)-ATPase activity.

How do metal cations affect the stability and structure of phospholipid bilayers? What role does ion binding play in the insertion of proteins and the overall mechanical stability of biological membranes? Investigators have used different theoretical and microscopic approaches to study the mechanical properties of lipid bilayers. Although they are crucial for such studies, molecular-dynamics simulations cannot yet span the complexity of biological membranes. In addition, there are still some experimental difficulties when it comes to testing the ion binding to lipid bilayers in an accurate way. Hence, there is a need to establish a new approach from the perspective of the nanometric scale, where most of the specific molecular phenomena take place. Atomic force microscopy has become an essential tool for examining the structure and behavior of lipid bilayers. In this work, we used force spectroscopy to quantitatively characterize nanomechanical resistance as a function of the electrolyte composition by means of a reliable molecular fingerprint that reveals itself as a repetitive jump in the approaching force curve. By systematically probing a set of bilayers of different composition immersed in electrolytes composed of a variety of monovalent and divalent metal cations, we were able to obtain a wealth of information showing that each ion makes an independent and important contribution to the gross mechanical resistance and its plastic properties. This work addresses the need to assess the effects of different ions on the structure of phospholipid membranes, and opens new avenues for characterizing the (nano)mechanical stability of membranes.

Measurements of very slow diffusive processes in membranes, like the diffusion of integral membrane proteins, by fluorescence recovery after photo bleaching (FRAP) are hampered by bleaching of the probe during the read out of the fluorescence recovery. In the limit of long observation time (very slow diffusion as in the case of large membrane proteins), this bleaching may cause errors to the recovery function and thus provides error-prone diffusion coefficients. In this work we present a new approach to a two-dimensional closed form analytical solution of the reaction-diffusion equation, based on the addition of a dissipative term to the conventional diffusion equation. The calculation was done assuming (i) a Gaussian laser beam profile for bleaching the spot and (ii) that the fluorescence intensity profile emerging from the spot can be approximated by a two-dimensional Gaussian. The detection scheme derived from the analytical solution allows for diffusion measurements without the constraint of observation bleaching. Recovery curves of experimental FRAP data obtained under non-negligible read-out bleaching for native membranes (rabbit endoplasmic reticulum) on a planar solid support showed excellent agreement with the analytical solution and allowed the calculation of the lipid diffusion coefficient.

Polarized attenuated total reflection Fourier transform infrared spectra were recorded on multilayer stacks of native gastric tubulovesicle membranes. The spectral intensity and linear dichroism were measured for average thicknesses ranging between 0 and 100 bilayers. Atomic force microscopy was used to investigate the orientation of the membranes at the top of the stack. Height profiles were obtained along randomly drawn lines and slopes were computed over various distances. Orientation distribution functions were obtained from the slopes and decomposed into Legendre polynomials. It was found that the second Legendre polynomials coefficient characterizing the membrane orientation was always larger than 0.9. It could therefore be concluded that the membrane tilt does not significantly contribute to the infrared dichroism, even for the largest thicknesses tested.

Hyperinsulinemia in myotonic dystrophy (MyD) is generally considered as a result of insulin resistance. However, as a consequence of abnormality in systemic membrane fluidity in this disease, abnormal insulin clearance or intrinsic pancreatic beta-cell dysfunction could also contribute to the hyperinsulinemia. To clarify the cause of hyperinsulinemia in MyD, we examined the insulin resistance, insulin clearance and the capacity of insulin secretion in 6 patients with MyD. They received a euglycemic hyperinsulinemic (insulin 40 mU/m2/min) clamp study for the quantification of insulin resistance by the glucose infusion rate (GIR). We evaluated their capacity of insulin secretion by the ratio of increment of serum insulin level to that of plasma glucose level 30 minutes after a 75 g oral glucose load (insulinogenic index; I.I.) and the ratio of area under the curve of serum insulin levels to that of plasma glucose levels during a 75 g oral glucose load (AUCIRI/AUCPG). The I.I. (1.1 +/- 0.6 vs 0.4 +/- 0.3, p < 0.05) and the AUCIRI/AUCPG (0.5 +/- 0.2 vs 0.2 +/- 0.1, p < 0.01) in MyD were significantly greater than those of GIR, body mass index and sex matched 6 non-diabetic controls respectively. Insulin clearance, estimated by the level of insulin and C-peptide before and during a euglycemic clamp study did not differ between the two groups. These results indicate that the postload hyperinsulinemia observed in MyD is not solely resulted from insulin resistance. Other factors, such as intrinsic beta-cell disorder may be involved.

Spectrofluorimetric methods allowing an estimation of the \"microviscosity\" (or the microfluidity) of synthetic and natural membranes may be used if the emissive phenomenon is dependent upon the cohesion of its local environment. Of the different methods that may be proposed, the study of the reactions between electronically excited molecules A*, which emit fluorescence, and B quenchers embedded in membranes, the rate constant of which is partly controlled by diffusion, are expected to inform about the values of diffusion coefficients of quenchers and therefore the \"microviscosity\" of the environment. Information may be improved when the product of the reaction between A* and B is itself emissive (excimers, exciplexes). We propose here that a kinetic model may apply this type of reaction when a process of static quenching occurs. The use of this kinetic model in studies carried out in this area should lead to a more accurate determination of the diffusion coefficients of A* and B, and therefore of the \"microviscosity\".

The influence of vinblastine (VLB) in combined chemotherapy on tumor cell membrane fluidity of a patient with exulcerated soft tissue sarcoma was studied by the electron paramagnetic resonance method (EPR). Tissue samples were taken before and after applications of VLB, Cis-Platinum (CDP) and combined intraarterial chemotherapy (IAC) and incubated with the spin probe, the palmitic acid methylester spin label analog, MeFasl (10, 3) incorporating into the cell membranes. EPR spectra of the labelled tissue samples were measured. Within few days after application of the chemotherapeutic drugs some oscillations of the membrane fluidity in the tissue were observed, while after a longer period of few weeks the relative amount of cells with greater membrane fluidity was found to decrease. Furthermore, an unexpected gradual increase in the EPR signal intensity after incubation of the tissue with the spin probe, probably due to an oxidative process in this particular sarcoma tissue was observed. These data could be useful for understanding of drug induced changes in cell membranes and for future timing of drug treatments in combined schedules.

Lecithin: cholesterol acyltransferase (LCAT) is an enzyme that catalyzes the esterifying reaction of cholesterol in plasma high density lipoprotein (HDL). Deficiency of LCAT is a rare hereditary disease characterized by several clinical symptoms such as proteinuria, corneal opacity, and anemia due to a shortened life span of erythrocytes. In this communication, we report a case of 40 year-old female patient of LCAT deficiency. She visited a hospital for work-up of proteinuria, corneal opacity and anemia. Activity of her serum LCAT was found to be extremely low, and characteristic changes in plasma lipids due to deficiency of LCAT was observed: those were marked decreases in HDL-cholesterol, degree of esterification in serum cholesterol, and apoprotein A-I, A-II, B and C-II levels. The diagnosis of LCAT deficiency was finally made. We studied about histopathological changes in the patient\'s kidney, and erythrocyte membrane lipid composition and fluidity. Histopathological findings in renal biopsy were follows: a) Light microscopy showed spherical deposits stained with periodic acid-Schiff in mesangial matrix and adjacent capillary loops, and hyaline deposits in arterioles, b) Electron microscopy showed vacuoles in mesangial matrix and along the glomerular basement membranes. In erythrocyte membrane lipids, increase of cholesterol to phospholipid molar ratio was evident, being accompanied by changes in phospholipid fractions: increase of phosphatidylcholine, and decreases of phosphatidylethanolamine, sphingomyelin and lysophosphatidylcholine. In phospholipid acyl chains, increase of C18:2 and decreased of C18:1 were evident in the patient. Erythrocyte membrane fluidity was found to be decreased in the patient in a measurement by pyrene, probably being related to the changes in membrane lipid composition.(ABSTRACT TRUNCATED AT 250 WORDS)