Nanoscale transport through permeabilizing structures in electrically stressed cell membranes

P. THOMAS VERNIER; ESIN SOZER; FEDERICA CASTELLANI; MARIA LAURA FERNANDEZ; MARCELO RISK

Praga

Simposio; 15th International Bioelectrics Symposium (BIOELECTRICS 2018); 2018

Institute of Plasma Physics of the Czech Academy of Sciences

Despite broad agreement that the pulsed-electric-fieldinducedpermeabilization of cell membranes involvesmore than the creation of lipid pores [1], reports of effortsto model and to investigate experimentally the complexityof the transport structures in the electropermeabilized cell(cf. Fig. 4 in [2]) are difficult to find. Here we discussprogress toward characterizing the permeabilizingstructures and processes (electropermeasomes) thatmake up the electropermeome [3].Molecular simulations of ion and small molecule transport through lipid electropores provideestimates of single pore conductance and the corresponding pore lifetimes and areal poredensities needed to align the properties of lipid pores with material transport observed inexperiments. Although these correlations are useful for calibrating molecular and continuummodels with laboratory observations, the lifetimes of lipid pores in molecular models (< 1 μs) aremuch too short to account for the persistent permeabilization (>> 1 s) that follows exposure ofcells to pulsed electric fields. To account for this, we propose a set of hypotheticalpermeabilizing structures, including evolved lipid pores, electro-modified membrane proteins,and other components of the stressed membrane, with pathways to experimental validation.New molecular simulations of interactions of ions with lipid pore walls that may contribute topore evolution are described, and results with mechanically constrained pores with longlifetimes are introduced for the first time.Recent experimental data present new inconsistentencies with the implicitly passive cellrepresented in the standard model of electroporation. A simple explanation is offered for thevery different transport patterns observed for cationic and anionic small fluorescent moleculesafter electropermeabilization. Electrically stressed cells, even though their membrane barrierfunction has been compromised, restore a non-zero resting potential very quickly afterelectroporating pulse exposures. Permeabilized cells fight back!