Photodynamic therapy: first responses

David Kessel; Michael Price

doi:10.1117/12.822140

13 July 2009 Photodynamic therapy: first responses

David Kessel, Michael Price

Proceedings Volume 7380, Photodynamic Therapy: Back to the Future; 738009 (2009) https://doi.org/10.1117/12.822140
Event: 12th World Congress of the International Photodynamic Association, 2009, Seattle, Washington, United States

Abstract

During the irradiation of photosensitized cells, reactive oxygen species (ROS) are generated leading to a variety of effects including apoptosis and autophagy. These responses can occur within minutes after irradiation. Apoptosis is an irreversible pathway to death that can be triggered by release of cytochrome c from mitochondria. Autophagy is a recycling process that can occur as a result of Bcl-2 photodamage or as a response to organelle disruption. We have reported that autophagy is associated with a 'shoulder' on the PDT dose-response curve. Although predominantly a survival pathway, autophagy can also play a role in cell death if cells attempt an excessive amount of recycling, beyond their ability to repair photodamage. Recent studies have been directed toward assessing the role of different ROS in the immediate response to PDT. While singlet oxygen is considered to be the major phototoxic ROS, it appears that catalase activity is also a determinant of the apoptotic response and that H₂O₂^•OH can amplify the effects of singlet oxygen. An early response to PDT also involves inhibition of membrane trafficking systems related to the endocytic pathway. The extent and nature of these early responses appear to be among the determinants of subsequent tumor eradication.

Citation Download Citation

David Kessel and Michael Price "Photodynamic therapy: first responses", Proc. SPIE 7380, Photodynamic Therapy: Back to the Future, 738009 (13 July 2009); https://doi.org/10.1117/12.822140

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KEYWORDS

Photodynamic therapy

Cell death

Proteins

Oxygen

Luminescence

Tumors

Leukemia

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