Bio-effects of ultrasound: Inhibitory effects on ultrasound induced apoptosis by cyclosporin A and fructose supplementation

To reveal the potential molecular interaction between mitochondrial permeability transition (MPT) and ultrasound induced apoptosis, hepatocarcinoma cells, HepG2, were treated by low intensity focused ultrasound in this study. Cyclosporin A (CSA), a special inhibitor of MPT, were pre-incubated with cells before ultrasound treatment, as well as fructose and pyruvate, respectively. Cell viability was measured by trypan blue dye exclusion test. The apoptosis was assessed by phosphatidylserine externalization and DNA fragmentation. The pattern of the decrease in mitochondrial trans-membrane potential (Δψ_m) was determined by flow cytometry. The optimal apoptosis with minimal lysis was attained with ultrasound at 5.0W/cm² for 1 min. In addition, apoptotic cells increased with increasing incubation time post-treatment and peaked at about 12 h. CSA maintained Δψ_m and reduced ultrasound-induced apoptosis, indicating MPT as the molecular mechanism required for apoptosis induced by ultrasound. Moreover, fructose supplementation also maintained Δψ_m and reduced ultrasound-induced apoptosis, while pyruvate didn't. It revealed glycolytic products of glycolysis, rather than those produced in tricarboxylic acid (TCA) cycle, were responsible for the reduction of apoptosis.