Apoptosis of THP-1 macrophages induced by protoporphyrin IX-mediated sonodynamic therapy

Abstract

Shuyuan Guo,1* Xin Sun,1,2* Jiali Cheng,1 Haobo Xu,1 Juhua Dan,2 Jing Shen,3 Qi Zhou,4 Yun Zhang,1 Lingli Meng,1 Wenwu Cao,4,5 Ye Tian1,2 1Division of Cardiology, the First Affiliated Hospital, Cardiovascular Institute, Harbin Medical University, Harbin, People's Republic of China; 2Division of Pathophysiology, the State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education, Harbin, People's Republic of China; 3Division of Oncology, the Third Affiliated Hospital, Harbin Medical University, Harbin, People's Republic of China; 4Laboratory of Photo- and Sono-theranostic Technologies and Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin, People's Republic of China; 5Department of Mathematics and Materials Research Institute, Pennsylvania State University, University Park, PA, USA *These authors contributed equally to this work Background: Sonodynamic therapy (SDT) was developed as a localized ultrasound-activated cytotoxic therapy for cancer. The ability of SDT to destroy target tissues selectively is especially appealing for atherosclerotic plaque, in which selective accumulation of the sonosensitizer, protoporphyrin IX (PpIX), had been demonstrated. Here we investigate the effects of PpIX-mediated SDT on macrophages, which are the main culprit in progression of atherosclerosis. Methods and results: Cultured THP-1 derived macrophages were incubated with PpIX. Fluorescence microscopy showed that the intracellular PpIX concentration increased with the concentration of PpIX in the incubation medium. MTT assay demonstrated that SDT with PpIX significantly decreased cell viability, and this effect increased with duration of ultrasound exposure and PpIX concentration. PpIX-mediated SDT induced both apoptosis and necrosis, and the maximum apoptosis to necrosis ratio was obtained after SDT with 20 µg/mL PpIX and five minutes of sonication. Production of intracellular singlet oxygen and secondary disruption of the cytoskeleton were also observed after SDT with PpIX. Conclusion: PpIX-mediated SDT had apoptotic effects on THP-1 macrophages via generation of intracellular singlet oxygen and disruption of the cytoskeleton. PpIX-mediated SDT may be a potential treatment to attenuate progression of atherosclerotic plaque. Keywords: sonodynamic therapy, protoporphyrin IX, atherosclerotic plaque, macrophage, singlet oxygen, cytoskeleton