Objectives Sonodynamic therapy (SDT) was developed as a localised ultrasound-activated cytotoxic therapy for cancers. The ability of SDT to destroy target tissues selectively is especially appealing for atherosclerotic plaque, where selective accumulation of sonosensitiser protoporphyrin IX (PpIX) had been proven. This study aims to evaluate the effects of PpIX mediated SDT on macrophages, which are the main culprit in atherosclerotic progression.
Methods Cultured THP-1 derived macrophages were incubated with diffferent concentrations of PpIX (1-50 μg/ml), and then exposed to the ultrasound for 0-15 minutes. Intracellular PpIX concentration was detected by fluorescence microscopy. Cell viability was measured by MTT assay. Hoechst 33342 and propidium iodide assay and flow cytometry analysis were performed to measure cell apoptosis and necrosis. Additionally, intracellular singlet oxygen (1O2) generation and cytoskeleton disruption were assessed.
Results Intracellular PpIX concentration increased with the concentration of PpIX in incubation medium. SDT with PpIX significantly decreased cell viability, and the effect increased with ultrasound exposure time and PpIX concentration. PpIX mediated SDT induced both apoptosis and necrosis, and the maximum apoptosis/necrosis ratio was obtained from SDT with 20 μg/ml PpIX and 5 minutes sonication. Intracellular 1O2 production and secondary cytoskeleton disruption were also observed after SDT.
Conclusions PpIX mediated SDT produced apoptotic effects on THP-1 macrophages, through intracellular 1O2 generation and cytoskeleton disruption. Therefore, PpIX mediated SDT can be a potential treatment for atherosclerotic plaque.