The protective role of PINK1/Parkin-mediated mitophagy in sonodynamic therapy

Abstract

Over the past years, several major treatments have been developed during the study of cancer therapies, such as radiotherapy, chemotherapy, and surgery (Al-Sarraf, LeBlanc et al. 1998, Huser, Michalski et al. 2008). Although these methods are significantly beneficial to patients, their drawbacks, such as therapeutic inefficiency and serious adverse effects, have prompted people to seek alternative treatments. Based on the synergistic effect of low-intensity ultrasound and sonosensitizer, sonodynamic therapy (SDT) is a promising non-invasive treatment of cancers, which has been demonstrated effective for different types of cancer cells (Rosenthal, Sostaric et al. 2004). Tumor cytotoxicity can be caused without damaging normal tissues by low intensity ultrasound combined with sonosensitizers (Dolmans, Fukumura et al. 2003). The therapeutic mechanism of SDT is generally understood by the production of ROS of sonosensitizer under the action of sound pressure (Li, Liu et al. 2012). However, the mitochondrial effect in SDT-induced cell death remains to be elucidated. In detail, selective mitochondrial autophagy, which is termed as "mitophagy", may be key to the cell death (Youle and Narendra 2011). Nevertheless, the operating principle of mitophagy in SDT is not entirely clear. In this study, treatment of MCF-7 cells with ALA-SDT, MTT test and PI/Annexin test has evaluated cell viability and apoptosis respectively. Confocal immunofluorescence microscopy is applied to detect mitophagy. Western blot and confocal immunofluorescence microscopy are used to detect mitochondrial dynamics and redox balance respectively. Parkin knockdown was applied to assess the mitophagy role in ALA-SDT-induced cell death. It is found that through mitochondrial depolarization and fragmentation and ALA-SDT could cause mitochondrial dysfunction and induce mitophagy. Furthermore, the signaling pathway depending on Parkin takes part in ALA-SDT-induced mitophagy and plays a "Protective umbrella" in killing cells induced by ALA- SDT. In the end, it is found that excessive production of ROS initiates mitophagy. In conclusions, ROS, the product of 5-ALA-SDT could result in mitophagy mediated by PINK1/Parkin. Mitophagy mediated by PINK1/Parkin may have a protective effect on 5-ALA-SDT-induced MCF-7 cell death.