CATIONIC LIPIDS DESTABILIZE LYSOSOMAL MEMBRANE IN-VITRO

Addition of cationic lipids to plasmid DNA considerably increases the efficiency of transfection. The mechanism has not yet been elucidated, A possibility is that these compounds destabilize biological membrane s (plasma, endosomal, lysosomal), facilitating the transfer of nucleic molecules through these membranes, We have investigated the problem b y determining if a cationic lipid -(1-(2,3-dioleoxy)propyl)-N,N,N,-tri methylammonium methyl-sulfate (DOTAP, Boehringer, Mannheim, Germany) a ffects the integrity of rat liver lysosomal membrane, We have measured the latency of beta-galactosidase, lysosomal enzyme, and found that i ncubation of lysosomes with low concentrations of DOTAP causes a strik ing increase in free activity of the hydrolase and even a release of t he enzyme into the medium, This indicates that lysosomal membrane is d eeply destabilized by the lipid, The phenomenon depends on pH, it is l ess pronounced at pH 5 than at pH 7.4. Anionic compounds, particularly anionic amphipathic lipids, can to some extent prevent this phenomeno n, It can be observed with various cationic lipids, A possible explana tion is that cationic liposomes interact with anionic lipids of lysoso mal membrane, allowing a fusion between the lipid bilayers which resul ts in a destabilization of the organelle membrane. (C) 1997 Federation of European Biochemical Societies.