Response and Deactivation of singlet oxygen by b-carotene in HeLa cells

GABRIELA BOSIO; JULIETA PARISI; MIGUEL REIGOSA; THOMAS BREITENBACH; PETER OGILBY; DANIEL MARTIRE

Brixen

Congreso; 2012 European Society For Photobiology, Photobiology School; 2011

Sociedad Europea de Fotobiología

We set out here to investigate the role of the nature of the photosensitizer and of the β -carotene concentration on the photoprotective effect of this carotenoid. For this purpose we investigated the viability, citotoxicity, and morphology of HeLa cells incubated with several photosensitizers upon different irradiation times with visible light. The photosensitizers used were the lypophilic porphyrins: 5,10,15,20-Tetraphenylporphin methyl-ester (TPPCOOMe) and Pyropheophorbide-a (PPa), and the hydrophylic porphyrin 5,10,15,20-Tetrakis(N-methyl-4-pyridyl)-21H, 23H-porphine (TMPyP) (Scheme 1). In order to ellucidate the possible photoprotective effect of β-carotene on cells containing the photosensitizers, MTT assays were also performed with cells previously incubated with this carotenoid. Clearly, signs of apoptosis are observed upon irrdiation of the cells containing any of the three photosensitiers. Mitochondrial activity assays (MTT) show cellular damage and only a photoprotective effect of β-carotene is observed in the concentration range 10-15 µM when TMPyP is used as the photosensitizer or at a concentration of 30 µM in experiments carried out with TPPCOOMe. At higher concentrations no photoprotective effect was observed.