Skin citotoxicity and apoptosis during acute UVB radiation: role of nitric oxide

DANIEL H. GONZÁLEZ MAGLIO; MARIELA L. PAZ; ANALÍA CZERNICZYNIEC; FEDERICO S. WEILL; JULIANA LEONI; JUANITA BUSTAMANTE

Buenos Aires, Argentina

Congreso; Society of Free Radical Research International, XII Biennial Meeting; 2004

Skin UVB irradiation activates constitutive and inducible NOS has been implicated with inflamatory diseases. Although keratinocytes are more resistant to UVB-induced apoptosis than other cells, molecular mechanisms of apoptosis are associated with UVB-citotoxicity. This study evaluate apoptosis and the role of mtNOS in an in vivo model of hairless mice between 8 and 72 hours after 200mJ/cm2 UVB irradiation. Skin biopsies (1 cm2) processed for haematoxilyn-eosin staining and 2.5 g of epidermal samples after treatment were homogenized and used for western blot analysis and TBARS determination. In addition oxygen uptake and mitochondrial nitric oxide synthase (mtNOS) activity were analysed from isolated mitochondria. Variation in size and morphology after irradiation were observed in the histological analysis, characterized by foci of individual keratinization and numerous atypic mitotic figures consisting with the presence of an inflamatory process. These results were associated with a 3.5 increase in epidermal iNOS expression. Decrease of 48% and 30% in succinate dependent state 3 and state 4 respiration rates respectively were observed, and malate-glutamate supported state 3 and 4 respiration rates were 43% and 53% respectively. Mitochondrial NO production was 39% increased after UVB. Interesting to observed was the decrease in TBARS levels after UVB irradiation. Evaluation of DNA fragmentation showed intense apoptotic cells in all of the dermal components. The results indicate that skin UVB irradiation is associated with skin morphological changes, increased apoptosis and alteration of mitochondrial metabolism with increased mtNOS activity.