Photomodification of Cardiac Membrane: Chaotic Currents and High Conductance States in Isolated Patches

Tarr, Merrill; Valenzeno, Dennis Paul

doi:10.1111/j.1751-1097.1998.tb09692.x

Cited by 6 publications

(1 citation statement)

References 26 publications

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“…These signals do not follow a repetitive pattern and are difficult to characterize by the typical parameters used to study ionic channels, such as mean current amplitude, open probability or dwell times. Instead, they resemble the current patterns observed on perturbed membranes of different kind of cells exposed to mechanical stress (42,43) or in cardiac cells stimulated by photosensitizer-generated reactive oxygen species (44). This characteristic signal can be observed in 6 out of 7 cells obtained from different samples of umbilical cords, although the effect of the peptide is variable in its magnitude.…”

Section: Cell Attached and Inside Out: Local Cell Permeabilizationmentioning

confidence: 51%

Arginine-Rich Peptides Destabilize the Plasma Membrane, Consistent with a Pore Formation Translocation Mechanism of Cell-Penetrating Peptides

Herce

Garcı́a

Litt

et al. 2009

Biophysical Journal

258

232

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Recent molecular-dynamics simulations have suggested that the arginine-rich HIV Tat peptides translocate by destabilizing and inducing transient pores in phospholipid bilayers. In this pathway for peptide translocation, Arg residues play a fundamental role not only in the binding of the peptide to the surface of the membrane, but also in the destabilization and nucleation of transient pores across the bilayer. Here we present a molecular-dynamics simulation of a peptide composed of nine Args (Arg-9) that shows that this peptide follows the same translocation pathway previously found for the Tat peptide. We test experimentally the hypothesis that transient pores open by measuring ionic currents across phospholipid bilayers and cell membranes through the pores induced by Arg-9 peptides. We find that Arg-9 peptides, in the presence of an electrostatic potential gradient, induce ionic currents across planar phospholipid bilayers, as well as in cultured osteosarcoma cells and human smooth muscle cells. Our results suggest that the mechanism of action of Arg-9 peptides involves the creation of transient pores in lipid bilayers and cell membranes.

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Section: Cell Attached and Inside Out: Local Cell Permeabilizationmentioning

confidence: 51%

Arginine-Rich Peptides Destabilize the Plasma Membrane, Consistent with a Pore Formation Translocation Mechanism of Cell-Penetrating Peptides

Herce

Garcı́a

Litt

et al. 2009

Biophysical Journal

258

232

View full text Add to dashboard Cite

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Functional Consequences of Oxidative Membrane Damage

2005

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The interaction of reactive oxygen species with biological membranes is known to produce a great variety of different functional modifications. Part of these modifications may be classified as direct effects. They are due to direct interaction of the reactive species with the molecular machinery under study with a subsequent chemical and functional modification of these molecules. An important part of the observed functional modifications are, however, indirect effects. They are the consequence of an oxidative modification of the environment of biological macromolecules. Lipid peroxidation-via its generation of chemically reactive products-contributes to the loss of cellular functions through the inactivation of membrane enzymes and even of cytoplasmic (i.e., water soluble) proteins. Oxidation of membrane lipids may, however, also increase the efficiency of membrane functions. This was observed for a series of transport systems. Lipid peroxidation was accompanied by activation of certain types of ion channels and ion carriers. The effect is due to an increase of the polarity of the membrane interior by accumulation of polar oxidation products. The concomitant change of the dielectric constant, which may be detected via the increase of the membrane capacitance, facilitates the opening of membrane channels and lowers the inner membrane barrier for the movement of ions across the membrane. The predominant effect, however, at least at a greater extent of lipid peroxidation, is the inhibition of membrane functions. The strong increase of the leak conductance contributes to the depolarization of the membrane potential, it destroys the barrier properties of the membrane and it may finally lead, via an increase of cytoplasmic Ca(2+) concentration, to cell death. The conclusions were derived from experiments performed with different systems: model systems in planar lipid membranes, native ion channels either reconstituted in lipid membranes or investigated in their natural environment by the patch-clamp method, and two important ion pumps, the Na/K-ATPase and the sarcoplasmic reticulum (SR) Ca-ATPase.

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Photomodification of the Electrical Properties of the Plasma Membrane: A Comparison Between 6 Different Membrane-Active Photosensitizers

2001

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The present study deals with photomodification of the electrical properties of the plasma membrane of an epithelial cell line (opossum kidney (OK) cells). The effect of photofrin II (previously investigated) is compared with that of 5 other membrane-active sensitizers: sulfonated Zn-phthalocyanine, merocyanine 540, rose bengal, methylene blue and protoporphyrin IX (an endogenous sensitizer induced by addition of its biosynthetic precursor 5-aminolaevulinic acid). The study was performed in order to investigate whether photomodification of the ion transport properties of the plasma membrane by membrane-active sensitizers is a general and early event in cellular photosensitization. The changes in the electrical properties were monitored by application of the whole-cell and the inside-out configuration of the patch-clamp technique. Illumination in the presence of the compounds (apart from merocyanine 540) gave rise to similar changes of the electrical properties of the membrane: depolarization of the membrane potential, inactivation of a large-conductance, Ca2+-dependent K+-channel (maxi-KCa), and a strong increase of the leak conductance of the membrane. This similarity indicates the general character of the functional photomodifications by membrane-active sensitizers previously reported for photofrin II.

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Photomodification of Cardiac Membrane: Chaotic Currents and High Conductance States in Isolated Patches

Cited by 6 publications

References 26 publications

Arginine-Rich Peptides Destabilize the Plasma Membrane, Consistent with a Pore Formation Translocation Mechanism of Cell-Penetrating Peptides

Arginine-Rich Peptides Destabilize the Plasma Membrane, Consistent with a Pore Formation Translocation Mechanism of Cell-Penetrating Peptides

Functional Consequences of Oxidative Membrane Damage

Photomodification of the Electrical Properties of the Plasma Membrane: A Comparison Between 6 Different Membrane-Active Photosensitizers

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