Effects of Steep Pulsed Electric Fields (SPEF) on Mitochondrial Transmembrane Potential of Human Liver Cancer Cell

Mitochondrial plays an important role in apoptosis, and measuring the change of mitochondrial transmembrane potential (DeltaPsi_m) is a useful method for apoptosis. Exposing human liver cancer cell SMMC-7721 dyed with Rhodamine 123 to steep pulsed electric fields (SPEF), this paper observed the real-time change of DeltaPsi_m using laser scanning confocal microscope (LSCM) to study the apoptosis effect of SPEF. The experiment results showed that DeltaPsi_m decreased gradually in process of exposing to SPEF, SPEF with higher voltage (600 V) and shorter width (100 ns) could cause a quicker decrease than SPEF with lower voltage (200 V) and longer width (1.3 mus). Such phenomenon kept up even after canceling SPEF, this may lead to collapse of DeltaPsi_m and induce apoptosis with tremendous possibilities. The experiment results of flow cytometry (SMMC-7721 dyed with Annexin V-FITC) approved that SPEF could induce apoptosis markedly (P<0.01); SPEF with lower voltage (200 V) and longer width (1.3 mus) could induce apoptosis more effectively (P<0.01) than SPEF with higher voltage (600 V) and shorter width (100 ns). These experiment results supply possible mechanism and parameter selection basis for tumor treatment using SPEF.