Photosensitization of nucleotides by pterins

GABRIELA PETROSELLI; ANDRÉS H.THOMAS; CAROLINA LORENTE; FRANCO M. CABRERIZO; ROSA ERRA-BASELLS; ALBERTO L. CAPPARELLI

Riezlern (Austria)

Workshop; Photochemie Optische Spektroskopie Sesorik; 2006

It is well known that UV radiation is mutagenic and carcinogenic, the mechanisms involved in DNA damage depending on the wavelength (1). UV-B radiation (290-320 nm) is absorbed by the DNA, whereas UV-A radiation (320-400 nm), representing a larger proportion of the solar UV radiation, is not absorbed by DNA, and damage to DNA is thought to involve photosensi­tized processes (2). Along these lines of reasoning, it is important to evaluate the capacity of endogenous substances to photoinduce DNA damage and to search and characterize compounds that might be involved in photosensitized processes leading to the generation of mutations in vivo.             Pterins are a family of heterocyclic compounds present in human cells, and in some diseases, like vitiligo, they are accumulated in zones of the skin devoid of melanin (3) and, therefore, with a deficiency of protection against UV radiation. Electronically excited states of pterins can be generated by radiation in the UV-A and visible spectral domain and are able to produce reactive oxygen species, such as singlet oxygen (1O2) that can oxidize DNA and other biomolecules.(4) In the present work, we describe pterin photosensitized reactions of nucleotides in both acidic and alkaline aqueous solutions. The production of reactive oxygen species and the role of 1O2 in these reactions are analyzed. (1) T.P. Coohil, M.J. Peak, J.G. Peak,  Photochem.Photobiol. 1987, 46, 1043-1050. (2) R.M. Tyrrell, S.M. Keyse,   J.Photochem.Photobiol. B: Biol. 1990, 4, 349-361. (3) K.U. Schallreuter, J.M. Wood, M.R. Pittelkow, M. Gütlich, K.R. Lemke, W. Rödl, N.N Swanson, K. Hitzemann, I. Ziegler,  Science 1994, 263, 1444–1448. (4) A.H. Thomas, C. Lorente, A.L. Capparelli, C.G. Martínez, A.M. Braun,  E. Oliveros, Photochem. Photobiol. Sci. 2003, 2, 245