Submitted August 2, 2006
Accepted January 30, 2007
The mitochondrial effects of novel apoptogenic molecules generated by psoralen photolysis as a crucial mechanism in PUVA therapy
Sergio Caffieri, Fabio Di Lisa, Federico Bolesani, Monica Facco, Gianpietro Semenzato, Francesco Dall'Acqua, and Marcella Canton*
Department of Pharmaceutical Sciences, University of Padova, Padova, Italy
Department of Biological Chemistry, University of Padova, Padova, Italy
Department of Clinical and Experimental Medicine, Hematology, and Clinical Immunology Branch, University of Padova, Padova, Italy
* Corresponding author; email: marcella.canton{at}unipd.it.
The generation of photoproducts of psoralen (POP) might be relevant in cell death induced by psoralen + UVA, namely PUVA, which is a recognized effective treatment for cutaneous T-cell lymphoma, chronic graft-versus-host disease and psoriasis. We investigated the occurrence of POP-induced cell death and the underlying mechanisms. POP were produced by irradiating a psoralen solution with UVA. Jurkat cells treated in the dark with these mixtures died mainly through an apoptotic mechanism. POP were separated by HPLC, and cells were added with each of these fractions. Two dimers of psoralen and 6-formyl-7-hydroxycoumarin (FHC) were identified in the apoptogenic fractions. Apoptosis was preceded by mitochondrial dysfunction caused by the opening of the mitochondrial permeability transition pore (PTP). In fact, both mitochondrial depolarization and cell death were prevented by the PTP inhibitor cyclosporin A (CsA). PTP opening was also documented in isolated mitochondria added with POP suggesting that apoptosis is caused by a direct effect of POP on mitochondria. In fact FHC alone induced PTP opening and CsA-inhibitable cell death of Jurkat cells whereas non-transformed T-lymphocytes were resistant. Along with identifying novel apoptogenic molecules, the present results indicate that POP generation directs transformed cells to apoptosis.
