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Journal of Environmental Pathology, Toxicology and Oncology

ISSN for PRINT: 0731-8898

Institutional price:	$672.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2006, Volume25

546 pages

Issue price - $344.00

Characterization of Apoptosis Induced by Photodynamic Treatment with Hypericin in A431 Human Epidermoid Carcinoma Cells

Juergen Berlanda
Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria

Tobias Kiesslich
Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria

Christian Benno Oberdanner
Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria

Franz Josef Obermair
Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria

Barbara Krammer
Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria

Kristjan Plaetzer
Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria

ABSTRACT

Hypericin is a naturally occurring metabolite extracted from Hypericum plants and is regarded as a promising photosensitizing agent for applications in the frame of photodynamic treatment (PDT). This treatment procedure is based on the light-induced formation of reactive oxygen species and subsequent destruction of target cells. We used an in vitro model system consisting of human epidermoid carcinoma cells (A431) and hypericin as a photosensitizer to study the time- and dose-dependent characteristics of hypericin-PDT-based induction of cytotoxicity and apoptotic cell death. The induction of apoptosis by hypericin-PDT was found to follow a strict dose-dependent manner with a transition to necrotic cell death at higher doses. Apoptosis was analyzed by characteristical biochemical and morphological markers (activation of caspases, nuclear fragmentation and membrane blebbing). Time-course analysis of an almost homogenous apoptotic population of cells (at 1.44 J/cm²) showed a rapid increase in nuclear fragmentation and activation of caspases reaching a maximum at 5 hr after irradiation. Using specific caspase substrates, significant activation of caspase-2, -3, -6, and -9 was found. Mitochondrial involvement during hypericin-PDT-induced apoptosis could be proven by a rapid reduction of the mitochondrial membrane potential; interestingly, the level of intracellular adenosine-5'-triphosphate (ATP) remains at control level for up to 6 hr post irradiation suggesting upregulation of glycolysis as a compensating mechanism of energy supply. Our data contribute to a deeper understanding of the processes involved in apoptotic cell death following photodynamic treatment with hypericin.