UV-B damage: a potential molecular play of Vitis vinifera L. extract

Ultraviolet component of sunlight UV-B (280-315 nm) is one of the major cause of skin damage. UV-B radiations have a low wavelength being absorbed almost completely by the epidermis; however, they interact directly with DNA causing molecular rearrangements. Photoaging and the development of skin cancer are of increasing relevance since lifestyle changes have led to an increase in the individual UV doses. Therefore, new prevention strategies have to be developed in order to reduce UV damage and delay photoaging process. In this context, different polyphenol-enriched botanicals have been proposed for the prevention of UV-mediated skin damage. Here it has been evaluated the antioxidant and DNA protective potential of an aqueous extracts of Vitis vinifera L., validated for the contents of anthocyanins, flavonoids and caffeic acid, against UV-B radiation in human keratinocyte (HaCaT) cell line. Treatment with the extract (100 μg/ml, 1h in serum-free media), was followed by the exposure to UV-B (20-30-40-80-160-320-640 mJ/cm2) radiation in PBS. The extract protects from the direct DNA damage induced by UV-B exposure even at doses where no oxidative damage was observed, as indicated by the alkaline comet and ɣH2AX tests, evaluated at T0 after the exposure. Moreover, it seems that the extract maintains the protective apoptotic pathway induced by UV-B. All these evidences led us to study the effect of the extract on DNA damage at molecular level, looking at the expression of genes involved in several pathways of DNA damage recognition, repair and apoptosis induction. Interestingly, the extract is able to modulate the expression of several genes involved both in damage signalling and NER (Nucleotide excision repair) pathway, mostly at 40 mJ/cm2 dose. The most important effect of the extract is on GADD45α especially at 40 and 80 mJ/cm2. This gene is pivotal in DNA repair pathway induced by UVR exposure, acting also on negative growth control. All together these findings suggest a potential interesting play of the extract also at the molecular level, modulating the expression of key genes involved in DNA damage signalling and repair.