Effect of various ultrasound insonifications on the Aβ-induced apoptotic neurons

Amyloid beta (Aβ) is a peptide that was known able to induce the apoptosis of nerve cells in the brain leading to the development of Alzheimer's disease (AD). In addition to providing medication treatment for the neurodegenerative disease, previous cell culture studies applying physical stimulations of a certain optical energy or low intensity ultrasound on the apoptotic cells have demonstrated that the viability of Ab-induced apoptotic neurons could be increased. Current study is to further explore insonification effects, such as frequency, exposure duration, and intensity on the apoptotic nerve cells and that the result is to provide a basic understanding about the therapeutic effects of ultrasound on the Ab-induced apoptotic neurons. Experiment were carried out using neuronal PC12 cells that were insonified by 1 MHz ultrasound with 20% duty cycle, 150 mW/cm₂ (SATA) for 3 minutes. After 72 hours, the viability and fate of cells were respectively evaluated by MTT assay and annexin V/PI double stain assay. Results showed that the stimulations by low intensity ultrasounds may contribute to the reduction of A-b induced cell apoptosis or necrosis. The effect of decreasing apoptotic cells tends to be apparent at a certain time depending on the condition of insonified ultrasounds. The variation of temperature in the cell plate was within 1°C throughout each insonification procedure. Thus, the effect on apoptotic PC12 cells may be largely due to the non- thermal effects of insonified ultrasound, which could enhance the permeability and other signal transduction pathways for cells.