OBJECTIVETo explore the role of Ca(2+) in nanosecond steep pulse (NSP)-induced apoptosis of human ovarian carcinoma cell line SKOV3 in vitro.

METHODSThe early apoptotic rate of SKOV3 cells treated with NSP was detected by Annexin V/PI double staining and flow cytometry. MTT assay was used to detect the viability of the cells pretreated with BAPTA-AM (0, 25, 50 and 100 µmol/L) chelation for 1 h to increase the intracellular free Ca(2+) prior to NSP exposure, and the cell morphological changes and caspase 12 expression were detected using Hoechst 33342 staining and Western blotting, respectively.

RESULTSFlow cytometry showed that NSP induced early apoptosis of SKOV3 cells, and the optimal effect was achieved with the treatment parameter configuration of field strength of 90 kV/cm, pulse width of 100 ns, frequency of 1 Hz, and exposure time of 30 s. The highest early apoptotic rate and necrosis rate was (60.31∓5.67)% and (1.35∓0.39)%, respectively. Pretreatment with BAPTA-AM chelation prior to NSP exposure significantly increased the cell viability (P<0.05), and resulted also in lowered apoptosis rate and decreased expression of caspase 12 (P<0.05).

CONCLUSIONNSP can induce apoptosis in SKOV3 cells. Increased intracellular free Ca(2+) functions as an important mediator in NSP-induced cell apoptosis, which may also involve Ca(2+)-mediated endo- plasmic reticulum pathway.