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Timing the multiple cell death pathways initiated by Rose Bengal acetate photodynamic therapy
E Panzarini1, V Inguscio, L Dini
1Department of Biological and Environmental Science and Technology (Di.S.Te.B.A.), University of Salento, Lecce 73100, Italy.
Abstract:
Rose Bengal acetate photodynamic therapy (RBAc-PDT) induced multiple cell death pathways in HeLa cells through ROS and ER stress. Indeed, apoptosis was the first preferred mechanism of death, and it was triggered by at least four different pathways, whose independent temporal activation ensures cell killing when one or several of the pathways are inactivated. Apoptosis occurred as early as 1 h after PDT through activation of intrinsic pathways, followed by activation of extrinsic, caspase-12-dependent and caspase-independent pathways, and by autophagy. The onset of the different apoptotic pathways and autophagy, that in our system had a pro-death role, was timed by determining the levels of caspases 9, 8, 3 and 12; Bcl-2 family; Hsp70; LC3B; GRP78 and phospho-eIF2α proteins. Interestingly, inhibition of one pathway, that is, caspase-9 (Z-LEHD-FMK), caspase-8 (Z-IETD-FMK), pan-caspases (Z-VAD-FMK), autophagy (3-MA) and necrosis (Nec-1), did not impair the activation of the others, suggesting that the independent onset of the different apoptotic pathways and autophagy did not occur in a subordinated manner. Altogether, our data indicate RBAc as a powerful photosensitiser that induces a prolonged cytotoxicity and time-related cell death onset by signals originating from or converging on almost all intracellular organelles. The fact that cancer cells can die through different mechanisms is a relevant clue in the choice and design of anticancer PDT.
Insights
Rose Bengal acetate photodynamic therapy (RBAc-PDT) triggers multiple, independent cell death pathways in HeLa cells, including apoptosis and autophagy. This multifaceted cell death mechanism enhances RBAc-PDT
Area of Science:
- Cell Biology
- Photodynamic Therapy
- Cancer Research
Background:
- Photodynamic therapy (PDT) is a promising cancer treatment modality.
- Understanding the precise mechanisms of cell death induced by PDT is crucial for optimizing its efficacy.
- Rose Bengal acetate (RBAc) is a photosensitizer used in PDT.
Purpose of the Study:
- To investigate the multiple cell death pathways induced by Rose Bengal acetate photodynamic therapy (RBAc-PDT) in HeLa cells.
- To elucidate the temporal activation and interdependencies of these cell death pathways.
- To assess the role of reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress in RBAc-PDT-induced cell death.
Main Methods:
- HeLa cells were treated with RBAc-PDT.
- Levels of key proteins involved in apoptosis (caspases 9, 8, 3, 12; Bcl-2 family), ER stress (GRP78, phospho-eIF2α), and autophagy (LC3B, Hsp70) were determined.
- Specific inhibitors were used to block apoptosis and autophagy pathways to assess their independence.
Main Results:
- RBAc-PDT induced multiple cell death pathways, primarily apoptosis and autophagy, mediated by ROS and ER stress.
- Apoptosis was initiated early (1 hour) via intrinsic pathways, followed by extrinsic, caspase-12-dependent, and caspase-independent pathways.
- Inhibition of individual pathways did not prevent the activation of others, indicating their independent temporal onset.
Conclusions:
- RBAc is a potent photosensitizer inducing prolonged cytotoxicity through diverse, independently activated cell death pathways.
- The activation of multiple cell death mechanisms, including apoptosis and autophagy, contributes to the overall effectiveness of RBAc-PDT.
- The ability of cancer cells to undergo death via multiple mechanisms is a key consideration for designing effective anticancer PDT strategies.
