Abstract
Pyropheophorbide-a methylester (PPME) is a second generation of photosensitizers used in photodynamic therapy (PDT). We demonstrated that PPME photosensitization triggered apoptosis of colon cancer cells as measured by using several classical parameters such as DNA laddering, PARP cleavage, caspase activation and mitochondrial release of cytochrome c. Preincubation of cells with N-acetyl cysteine (NAC) or pyrolidine dithiocarbamate (PDTC) protected against apoptosis mediated by PPME photosensitization showing that reactive oxygen species (ROS) are involved as second messengers. On the other hand, photosensitization carried out in the presence of deuterium oxide (D2O) which enhances singlet oxygen (1O2) lifetime only increases necrosis without affecting apoptosis. Since PPME was localized in the endoplasmic reticulum (ER)/Golgi system and lysosomes, other messengers than ROS were tested such as calcium, Bid, Bap31, phosphorylated Bcl-2 and caspase-12 but none was clearly identified as being involved in triggering cytochrome c release from mitochondria. On the other hand, we demonstrated that the transduction pathways leading to NF-kappaB activation and apoptosis were clearly independent although NF-kappaB was shown to counteract apoptosis mediated by PPME photosensitization.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetylcysteine / pharmacology
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Adenocarcinoma / pathology*
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Antioxidants / pharmacology
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Apoptosis / drug effects*
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Caspase 3
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Caspases / metabolism
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Ceramides / physiology
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Chloroquine / pharmacology
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Colonic Neoplasms / pathology*
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Cytochrome c Group / metabolism
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Deuterium Oxide / pharmacology
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Endoplasmic Reticulum / metabolism
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Gene Expression Regulation, Neoplastic / drug effects
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Gene Expression Regulation, Neoplastic / radiation effects
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Golgi Apparatus / metabolism
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Humans
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Lysosomes / metabolism
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Mannans / pharmacology*
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Mannosephosphates / pharmacology*
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Microscopy, Fluorescence
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Mitochondria / physiology
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NF-kappa B / metabolism
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Oxidation-Reduction
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Oxidative Stress
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Oxygen / metabolism
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Phosphorylation
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Photochemistry
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Photosensitizing Agents / pharmacology*
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Proline / analogs & derivatives
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Proline / pharmacology
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Protein Processing, Post-Translational
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Radiation Tolerance
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Radiation-Protective Agents / pharmacology
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Reactive Oxygen Species
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Second Messenger Systems
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Singlet Oxygen
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Thiocarbamates / pharmacology
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Tumor Cells, Cultured
Substances
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Antioxidants
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Ceramides
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Cytochrome c Group
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Mannans
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Mannosephosphates
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NF-kappa B
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Photosensitizing Agents
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Proto-Oncogene Proteins c-bcl-2
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Radiation-Protective Agents
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Reactive Oxygen Species
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Thiocarbamates
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prolinedithiocarbamate
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Singlet Oxygen
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mannose-6-phosphate rich phosphomannan
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Chloroquine
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Proline
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CASP3 protein, human
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Caspase 3
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Caspases
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Deuterium Oxide
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Oxygen
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Acetylcysteine