title: The PARP inhibitor PJ-34 sensitizes cells to UVA-induced phototoxicity by a PARP independent mechanism.
abstract: A combination of a photosensitizer with light of matching wavelength is a common treatment modality in various diseases including psoriasis, atopic dermatitis and tumors. DNA damage and production of reactive oxygen intermediates may impact pathological cellular functions and viability. Here we set out to investigate the role of the nuclear DNA nick sensor enzyme poly(ADP-ribose) polymerase 1 in photochemical treatment (PCT)-induced tumor cell killing. We found that silencing PARP-1 or inhibition of its enzymatic activity with Veliparib had no significant effect on the viability of A431 cells exposed to 8-methoxypsoralen (8-MOP) and UVA (2.5J/cm(2)) indicating that PARP-1 is not likely to be a key player in either cell survival or cell death of PCT-exposed cells. Interestingly, however, another commonly used PARP inhibitor PJ-34 proved to be a photosensitizer with potency equal to 8-MOP. Irradiation of PJ-34 with UVA caused changes both in the UV absorption and in the 1H NMR spectra of the compound with the latter suggesting UVA-induced formation of tautomeric forms of the compound. Characterization of the photosensitizing effect revealed that PJ-34+UVA triggers overproduction of reactive oxygen species, induces DNA damage, activation of caspase 3 and caspase 8 and internucleosomal DNA fragmentation. Cell death in this model could not be prevented by antioxidants (ascorbic acid, trolox, glutathione, gallotannin or cell permeable superoxide dismutase or catalase) but could be suppressed by inhibitors of caspase-3 and -8. In conclusion, PJ-34 is a photosensitizer and PJ-34+UVA causes DNA damage and caspase-mediated cell death independently of PARP-1 inhibition.
authors.affiliation: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors.forename: Petra
authors.initials: P
authors.lastname: Lakatos
authors.affiliation: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Hegedűs
authors.affiliation: Department of Biology, Faculty of Sciences, Universidad Autónoma of Madrid, 28049-Madrid, Spain.
authors.forename: Nerea
authors.initials: N
authors.lastname: Salazar Ayestarán
authors.affiliation: Department of Biology, Faculty of Sciences, Universidad Autónoma of Madrid, 28049-Madrid, Spain.
authors.forename: Ángeles
authors.initials: Á
authors.lastname: Juarranz
authors.affiliation: Department of Inorganic and Analytical Chemistry, Faculty of Sciences, University of Debrecen, Debrecen, Hungary.
authors.forename: Katalin E
authors.initials: KE
authors.lastname: Kövér
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors.forename: Éva
authors.initials: É
authors.lastname: Szabó
authors.affiliation: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; MTA-DE Cell Biology and Signaling Research Group, Debrecen, Hungary. Electronic address: lvirag@med.unideb.hu.
authors.forename: László
authors.initials: L
authors.lastname: Virág
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D020552:Comet Assay; D004249:DNA Damage; D020868:Gene Silencing; D006801:Humans; D010616:Phenanthrenes / Q000494:pharmacology*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D000071137:Poly (ADP-Ribose) Polymerase-1 / Q000235:genetics / Q000378:metabolism*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D018874:Spheroids, Cellular / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: C434926:N-(oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide hydrochloride; D010616:Phenanthrenes; D017319:Photosensitizing Agents; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D020169:Caspases
keywords: Apoptosis; Cell death; Poly(ADP-ribose) polymerase-1; Poly(ADP-ribosyl)ation; Spheroid; Ultraviolet light