Apoptosis of SMMC-7721 cells induced by the low-intensity pulsed ultrasound in vitro / 中华物理医学与康复杂志

ABSTRACT

Objective To explore whether the low-intensity pulsed ultrasound (LIPU) could induce apoptosis on SMMC-7721 cells and to explore the underlying mechanism.Methods The SMMC-7721 cells were randomly divided into 4 groupsa blank control group,which was subject to sham exposure to ultrasound,and 3 ultrasound intervention groups exposed to ultrasound at intensities of 0.5,1.3 and 2.0 W/cm2,respectively.Then they were incubated for 6 h.The cell apoptosis,necrosis and changes of cell cycles were measured using the flow cytometry.The transmission electron microscope (TEM) was used to observe microstructural changes in the cells.The agarose gel electrophoresis (AGE) was used to examine the DNA fragmentation,and Western-blotting was employed to assess the protein expression of caspase-3.Results The average cell apoptosis rate of the 3 intervention groups were 4.66％,8.99％ and 32.41％,respectively.The percentage of cells in G2 phase increased significantly and those in G1 phase decreased significantly in the 3 intervention groups compared to the blank control group at the same time points.In the intervention groups,significant cell apoptosis was observed under TEM,and DNA ladders was seen in AGE,with DNA fragments appearing obviously when cells were incubated for 6 h and 9 h after ultrasound exposure.In intervention groups subject to 1.3 and 2.0 W/cm2 ultrasound exposure,the protein expression of caspase-3 was significantly higher than that of the control group.Conclusion LIPU can inhibit the proliferation and induce apoptosis of SMMC-7721 cells with a dose-dependent feature.The possible mechanism underlying the LIPU-induced cell apoptosis might be related to the activation of the mitochondria pathway,and especially the caspase-3 protein.