Modulation of calcium signaling by nanosecond electric pulses and cell death through apoptosis in A549 lung cancerous cells

Calcium ion (Ca²⁺), which serves as one of the important signaling agents, is imperative to control normal cell function. The altered Ca²⁺ signaling is known to play a crucial role in the resistance of cancerous cells against apoptosis. Herein, nanosecond pulsed electric field (nsPEF) was applied to non-small lung cancerous cells A549, and Ca²⁺ mobilization along with mitochondria-mediated apoptotic cell death that accompanies morphological changes was investigated. In the presence of nsPEF, intracellular mobilization of Ca²⁺ ions through the efflux from endoplasmic reticulum storage was dependent on the pulse-width of the applied field. The field-induced Ca²⁺ mobilization has shown to correlate with the superoxide anion (O₂⁻) generation, which probably occurred in mitochondria utilizing the nicotinamide adenine dinucleotide (NADH), as supported by the field-induced change in autofluorescence intensity and lifetime of NADH. Mitochondrial dysfunction and O₂⁻ generation, which promoted apoptotic cell death, were also induced by nsPEF with strong correlation with intracellular Ca²⁺ ions.