Control by membrane order of voltage-induced permeabilization, loading and gene 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 membrane leading to DNA and protein transfers. A key step, in the interaction between macromolecules and the electropermeabilized membrane, is involved. We previously reported that membrane and DNA associated hydration and undulation 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), molecules known to affect membrane order and therefore undulation forces, were investigated on Chinese hamster ovary (CHO) cells. We used millisecond square wave pulses, conditions giving high efficiency for gene transfer. No effect was observed on cell permeabilization for small sized molecules. Only little change on electroloading of proteins such as R-phycoerythrin was obtained in presence of EtOH. But, a decrease (increase) in electrotransfection was observed for cells treated with EtOH (lyso-PC). Under our conditions, no additional effects of the chemical treatment were observed on cell viability and on membrane resealing. These results tentatively explained in terms of the effect of membrane order on membrane organization and interaction between molecules and membrane supports the existence of the plasmid-membrane interaction in the mechanism of electrically mediated gene transfer.