Incorporation and photodynamic activity of pterin in HeLa cells

M. PAULA DENOFRIO; SONJA HATZ; FRANCO M. CABRERIZO; MERETE K. RARUP; ANDRES H. THOMAS; PETER R. OGILBY; CAROLINA LORENTE

St.Petersburg, Florida, USA

Congreso; 19th I-APS (Inter-American Photochemical Society) Conference on Photochemistry; 2009

The participation of pterins in different photobiological processes has been suggested or demonstrated in past decades, and interest in the photophysics and photochemistry of this group of compounds has subsequently increased. The photophysics and photochemistry of the pterin (Ptr) moiety has recently been investigated.[1] Ptr is photostable in the absence of O2, whereas excitation in air equilibrated solution leads to oxidation, yielding non-pterinic photoproducts. However, the quantum yields of Ptr disappearance in the presence of O2 are much lower than those corresponding to derivatives bearing oxidizable substituents. Most pterins are good singlet molecular oxygen (1O2) sensitizers, under UV-A irradiation in aqueous solutions.[2] In addition, Ptr acts as sensitizer in photochemical reactions that induce DNA damage[3],[4] In order to assess the photodynamic capability of Ptr, in this work we have performed experiments using a cell line derived from cervical cancer cells (HeLa) as targets. The irradiation of eukaryotic cell lines, like HeLa, in the presence of a given photosensitizer allows to investigate if photoinduced processes has real effects at cellular level. In experiments performed using HeLa cells incubated in the presence of Ptr, the study of the cell extract by fluorescence spectroscopy suggest that Ptr uptake occurred. After irradiation with UV-A light, analysis with Rhodamine 123 and Trypan Blue assays showed a decrease in the viability of the Ptr-treated HeLa cells, whereas this effect was not observed in the controls. [1] C. Lorente, A.H. Thomas Acc. Chem. Res. 39, 2006, 395. [2] A.H. Thomas, C. Lorente, A.L. Capparelli, C.G. Martínez, A.M. Braun, E. Oliveros, Photochem. Photobiol. Sci. 2, 2003, 245. [3] Ito, K.; Kawanishi, S. Biochemistry 36, 1997, 1774. [4] Lorente, C.; Thomas, A. H.; Villata, L. S.; Hozbor, D.; Lagares, A.; Capparelli, A. L. Pteridines  11, 2000, 100.