Multifunctional photosensitizers for the activation and visualization of pyroptotic cell death under photodynamic therapy

To understand interorganelle interactions related to cell death in the complex cellular context, analysis with a single compound that possesses multiple functions is more informative than analysis after treatment with several compounds at the same time due to the different rates of cellular uptake and metabolism of each compound. Here, we report MPBA14+, a dual-organelle-targeting probe with selective photosensitizing activity. Cell images obtained by confocal laser scanning microscopy (CLSM) demonstrated that MPBA14+ selectively localized in lipid droplets (LDs) and mitochondria, which allowed monitoring of the interactions of LDs and mitochondria by live-cell imaging. In particular, the number of peridroplet mitochondria (PDM) was found to be increased under various metabolic stress conditions via analysis with MPBA14+. Moreover, MPBA14+ treatment in conjunction with light irradiation induced pyroptosis, a recently identified type of proinflammatory cell death, mediated by mitochondrial dysfunction due to the selective production of reactive oxygen species (ROS). The stable fluorescence emitted by MPBA14+ even in damaged mitochondria enabled live-cell imaging analysis of changes in LDs, mitochondria, and PDM via photodynamic therapy (PDT). Our results show the potential of MPBA14+ as a multifunctional photosensitizer that can contribute to the establishment of subcellular organelle-targeted PDT that induces immunogenic pyroptosis of tumor cells.

Automated summary

In this study, we developed a dual-organelle-targeting probe called MPBA14+ with selective photosensitizing activity. Through live-cell imaging analysis, we found that MPBA14+ selectively localized in lipid droplets (LDs) and mitochondria, enabling monitoring of their interactions. Additionally, MPBA14+ was shown to induce a recently identified type of proinflammatory cell death called pyroptosis, mediated by mitochondrial dysfunction. The stable fluorescence emitted by MPBA14+ allowed for live-cell imaging analysis of changes in LDs, mitochondria, and peridroplet mitochondria (PDM) via photodynamic therapy (PDT).