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

Abstract

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.

Inactivation ofPlasmodium falciparumby Photodynamic Excitation of Heme‐Cycle Intermediates Derived from δ‐Aminolevulinic Acid

“…This report, coupled with our observation, by use of fluorescence microscopy, that uninfected erythrocytes do not reveal detectable photosensitizer, suggests that potentially damaging levels of protoporphyrins only accumulate in parasitized erythrocytes, and not in uninfected RBCs, in which heme biosynthesis is tightly controlled. In addition, since oxidative damage is often manifested by disruptions to erythrocyte-membrane integrity [61] and since merozoites of Plasmodium species require specific erythrocyte receptors and are extremely selective in their choice of erythrocyte [62], our observation that merozoites of P. falciparum could invade and mature within RBCs treated with ALA and exposed to light suggests that any PPIX activity in uninfected cells probably does not adversely affect erythrocyte viability.…”

Xanthene Dyes Induce Membrane Permeabilization of Bacteria and Erythrocytes by Photoinactivation

“…7), was attributable to the low ability to produce singlet oxygen (Table 2). Of course, the permeability‐increasing action of dyes is not limited to bacteria and erythrocytes alone, and rose bengal is reported to cause an increase in the permeability of the plasma membrane of kidney cells or cardiac myocytes (10,11). Interestingly, a good correlation between increases in membrane permeability and the dissipation of membrane potential was also observed in kidney cells (11).…”

Modifying excitation light dose of novel photosensitizer PVP-Hypericin for photodynamic diagnosis and therapy

“…It has been reported by Stephens and Allan [6] as well as Goldman and Spector [7] that cells may have intrinsic enzymatic mechanisms for converting ROS to less harmful compounds, so as long as these systems are not saturated, cells tolerate generated ROS. Immoderate generation of ROS leads to oxidative stress which can cause apoptosis, necrosis or autophagy-associated cell death [7][8][9]. Therefore, according to the above explanation, the opportunity for prolonged detection and diagnostic imaging of cancer cells needs low photobleaching and thus a low level of excitation [5,[10][11][12].…”