In this study, we report evidence of the damage effects of sonodynamic
therapy (SDT) on a novel intracellular target, cytoskeletal
F-actin, that has great importance for
cancer treatment. Ehrlich
ascites carcinoma (EAC) cells suspended in PBS were exposed to ultrasound at 1.34 MHz for up to 60s in the presence and absence of
protoporphyrin IX (
PPIX). To evaluate the polymeric state and distribution of actin filaments (AF) we employed
FITC-
Phalloidin staining. The percentage of cells with intact AF was decreased with 10-80 microM
PPIX after ultrasonic exposure, while only few cells with disturbed
F-actin were observed with 80 microM
PPIX alone. The fluorescence intensity of
FITC-
Phalloidin labeled cells was detected by flow cytometry. The morphological changes of EAC cells were observed by scanning electron microscope (SEM). The nuclei were stained with
Hoechst 33258 to determine apoptosis. Cytoskeletal
F-actin and cell morphological changes were dependent on the time after SDT. Some cells suffered deformations of plasma membrane as
blebs that reacted positively to
FITC-
Phalloidin at 2h after SDT treatment. Many of the cells showed the typically apoptotic
chromatin fragmentation. The alterations were more significant 4h later. Our results showed that cytoskeletal
F-actin might represent an important target for the SDT treatment and the observed effect on
F-actin and the subsequent
bleb formation mainly due to apoptosis formation due to the treatment.