Control by membrane order of voltage-induced permeabilization, loading andgene transfer in mammalian cells

Cells can be transiently permeabilized by application of electric pulses. A direct consequence of this treatment is to create a new state in the membr ane leading to DNA and protein transfers. A key step, in the interaction be tween macromolecules and the electropermeabilized membrane, is involved. We previously reported that membrane and DNA associated hydration and undulat ion forces appeared to be involved in this process by studying the effects of osmotic pressure. Effects of ethanol (EtOH) and L-alpha -lysophosphatidylcholine (lyso-PC), m olecules known to affect membrane order and therefore undulation forces, we re investigated on Chinese hamster ovary (CHO) cells. We used millisecond s quare wave pulses, conditions giving high efficiency for gene transfer. No effect was observed on cell permeabilization for small sized molecules. Onl y little change on electroloading of proteins such as R-phycoerythrin was o btained in presence of EtOH. But, a decrease (increase) in electrotransfect ion was observed for cells treated with EtOH (lyso-PC). Under our condition s, no additional effects of the chemical treatment were observed on cell vi ability and on membrane resealing. These results tentatively explained in t erms of the effect of membrane order on membrane organization and interacti on between molecules and membrane supports the existence of the plasmid-mem brane interaction in the mechanism of electrically mediated gene transfer. (C) 2000 Elsevier Science S.A. All rights reserved.