Ca2+-dependent permeabilization of mitochondria and liposomes by palmitic and oleic acids: A comparative study

In the present work, we examine and compare the effects of saturated (palmitic) and unsaturated (oleic) fatty acids in relation to their ability to cause the Ca2+-dependent membrane permeabilization. The results obtained can be summarized as follows. (I) Oleic acid (OA) permeabilizes liposomal membranes at much higher concentrations of Ca2+ than palmitic acid (PA): 1 mM versus 100 AM respectively. (2) The OA/Ca2+-induced permeabilization of liposomes is not accompanied by changes in the phase state of lipid bilayer, in contrast to what is observed with PA and Ca2+. (3) The addition of Ca2+ to the PA-containing vesicles does not change their size; in the case of OA, it leads to the appearance of larger and smaller vesicles, with larger vesicles dominating. This can be interpreted as a result of fusion and fission of liposomes. (4) Like PA, OA is able to induce a Ca2+-dependent high-amplitude swelling of mitochondria, yet it requires higher concentrations of Ca2+ (30 and 100 mu M for PA and OA respectively). (5) In contrast to PA, OA is unable to cause the Ca2+-dependent high-amplitude swelling of mitoplasts, suggesting that the cause of OA/Ca2+-induced permeability transition in mitochondria may be the fusion of the inner and outer mitochondrial membranes. (6) The presence of OA enhances PA/Ca2+-induced permeabilization of liposomes and mitochondria. The paper discusses possible mechanisms of PA/Ca2+- and OA/Ca2+-induced membrane permeabilization, the probability of these mechanisms to be realized in the cell, and their possible physiological role. (C) 2014 Elsevier B.V. All rights reserved.