by Mauricio Baptista
On the recent years, we aimed to understand the effects of visible light on skin and hair. We showed that melanin is able to photosensitize the generation of singlet oxygen both in the UVA (355nm) and in the visible (532nm) with similar yields and that the photosensitization of melanin forming singlet oxygen is the main cause of damage in hairs under exposition to visible light . These results also suggest the possible role of visible light in damaging human skin, similarly to the well accepted effect of UVA light. In order to understand the effects of the photoinduced melanin reactions on human skin, we compared the effect of visible light on two melanocyte cell lines: one of them producing lots of intracellular melanin and the other just a natural amount. These results were recently published in .
By quantifying the amount of singlet oxygen production by its characteristic emission at 1270nm, we showed that intracellular melanin leads to an increased level of intracellular singlet oxygen generation. We also wanted to prove that the singlet oxygen generation by melanin photosensitization is able to cause direct damage on nuclear DNA. Therefore, we performed a comet assay and we observed that in the presence of melanin and visible light there clearly is Fpg and Endo III-sensitive modifications. The presence of strand breaks after the treatment with Fpg and Endo III, demonstrated that melanin photosensitization by visible irradiation induces direct oxidative damage to nuclear DNA. he ratio of Fpg- to Endo III-sensitive modifications indicated that oxidative damage in DNA is most likely due to both type II and type I mechanisms.
Clearly, visible light affects skin health, but people are encouraged to stay under the sun if they use sufficient amounts of ‘‘good sunscreen’’ (i.e., sunscreens that provide effective protection against UVA and UVB). This recommendation is clearly a mistake because it ignores the effects of visible light, which penetrates more deeply into skin than does UVB and UVA. We hope our research will stimulate the development of new comprehensive strategies of skin protection that also considers the effect of visible light.
- O. Chiarelli-Neto, C. Pavani, A. S. Ferreira, A. F. Uchoa, D. Severino, M. S. Baptista
Generation and suppression of singlet oxygen in hair by photosensitization of melanin.
Free Radical Biology and Medicine, 51 (6): 1195-202, 2011. | http://dx.doi.org/10.1016/j.freeradbiomed.2011.06.013
- O. Chiarelli-Neto, A. S. Ferreira, W. K. Martins, C. Pavani, D. Severino, F. Faião-Flores, S. S. Maria-Engler, E. Aliprandini, G. R. Martinez, P. Di Mascio, M. H. G. Medeiros, M. S. Baptista
Melanin photosensitization and the effect of visible light on epithelial cells.
PLoS One, 9: e113266, 2014. | http://dx.doi.org/10.1371/journal.pone.0113266
Mauricio da Silva Baptista, PhD.
Professor at Department of Biochemistry,
Institute of Chemistry, University of São Paulo, Brazil