Investigations into the Correlation Properties of Membrane Electroporation-Induced Inward Currents: Prediction of Pore Formation

Abstract

Membrane electroporation (MEP) induces a drastic change in membrane conductance and permeability. However, the underlying mechanisms by which MEP-induced currents (I(MEP)) are generated or resealed remain unclear. In this study, we investigated how the fluctuations of I(MEP) might be elicited in different types of cells, including pituitary GH(3) cells, NG108-15 neuronal cells, and RAW 264.7 macrophages. We applied the detrended fluctuation analysis (DFA) to analyze the current signals in response to large hyperpolarizations. The DFA exponents from the current signals at 10 s preceding the start of the initial I(MEP) (I(Pre)) in GH(3) cells exhibited two components (short time lag [α(1)] and long time lag [α(2)]) with a crossover threshold of about 7 ms. The α(1) value was 0.46 ± 0.04 (n = 7), whereas the α(2) value with 0.62 ± 0.05 (n = 7) indicated the presence of long-term correlations of current signals. However, during maximal I(MEP), the slope of double logarithmic plot was linear and estimated to be 0.99 ± 0.02 (n = 8) with no clear crossover. Upon changes in membrane polarization, neither short- nor long-range correlation was altered. Chloroquine (CQ), a lysosomotropic agent, decreased the I(MEP) amplitude with an IC(50) value of 46 μM; however, it had no effects on the scaling exponents of I(Pre) or I(MEP). Although CQ or membrane polarization altered the amplitudes of I(MEP), no changes in correlation properties of this current were detected. The scaling exponents derived from I(Pre) exhibit long-range correlations in these different types of cells, indicating there is a correlated character of the electropore dynamics that may be allowed to predict the MEP process.

Identification of Minuscule Inward Currents as Precursors to Membrane Electroporation-Induced Currents: Real-Time Prediction of Pore Appearance

“…They had a resistance of 3-5 MΩ when filled with different pipette solutions described above. Ion currents were measured with glass pipettes in whole-cell configuration of standard patch-clamp technique by means of an RK-400 amplifier (Bio-Logic, Claix, France) [9,11]. …”

“…The non-linear least-squares fitting was made in the Solver-add-in bundled with Microsoft Excel 2007 [9,11,25]. The I MEP amplitudes were generally taken about 2 min after the voltage protocol was repetitively applied to the cell.…”

“…The I MEP amplitudes were generally taken about 2 min after the voltage protocol was repetitively applied to the cell. The latency to I MEP generation is Gaussian normal distribution with mean value of 68±7 sec when cells were repetitively hyperpolarized from -80 to -200 mV [11]. …”

“…Additionally, owing to high conductance of MEP-induced channels, even at low probability of opening, significant currents tend to flow, thereby altering the electrical behavior of cells [1,2,6,7,8]. Recent work in our laboratory has characterized the electrical properties of MEP-induced currents ( I MEP ) in different types of cells [9,10,11,12]. Besides that, despite numerous experimental and theoretical studies, many aspects of MEP-induced currents ( I MEP ) remain elusive.…”

“…The detrended fluctuation analysis has been previously applied to analyze the scaling exponents in the time series of I MEP [11]. However, its real-time computation capacity used to herald the coming of pore appearance is limited.…”