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Photoprotective effect of Calluna vulgaris extract against UVB-induced phototoxicity in human immortalized keratinocytes.

There is an increasing interest in the use of natural antioxidants as photoprotective agents against skin damages produced by ultraviolet radiation. The aim of our study was to investigate the protective effect of a Calluna vulgaris extract in human keratinocytes (HaCaT) exposed to ultraviolet B (UVB) radiation. HaCaT cells were treated with C. vulgaris extract 30 minutes prior to irradiation with UVB. The protective effect was evaluated by assessing cell viability using tetrasolium salt (MTT) assay; the generation of lipid peroxides was evaluated using malondialdehide assay (MDA); and DNA damage was evaluated using the comet assay and the quantification by ELISA of specific DNA photolesions [i.e., cyclobutane-pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs)]. After irradiation with cytotoxic doses of UVB (300 and 500 mJ/cm(2)), HaCaT cells pretreated with C. vulgaris extract (50 μg GAE/ml) showed significantly increased viability compared to control cells exposed to UVB only. Irradiation alone increased MDA levels in a dose-dependent fashion. Pretreatment with 12 μg GAE/ml extract lowered MDA levels both at 100 mJ/cm(2) (ρ<0.01) and 300 mJ/cm(2) (ρ<0.001). Treatment with C. vulgaris extract before exposure to UVB also reduced DNA damage: Lesion scores in a comet assay were significantly reduced at UVB doses of 50 mJ/cm2 (ρ<0.01) and 100 mJ/cm(2) (ρ<0.05), while CPDs and 6-4PPs (via ELISA) were significantly lower after irradiation with 100 mJ/cm(2) in the protected cells (ρ<0.05 for CPDs and ρ<0.001 for 6-4PPs). These results recommend the use of the C. vulgaris extract as photoprotective agent, in combination with sunscreens and/or other natural products with similar or complementary properties.