Effects of native and particulate polyphenols on DNA damage and cell viability after UV-C exposure.

Plant polyphenols have poor water solubility, resulting in low bioavailability. In order to overcome this limitation, the drug molecules can be coated with multiple layers of polymeric materials. Microcrystals of quercetin and resveratrol coated with a (PAH/PSS)4 or (CH/DexS)4 shell were prepared using the layer-by-layer assembly method; cultured human HaCaT keratinocytes were treated with UV-C, and after that, cells were incubated with native and particulate polyphenols. DNA damage, cell viability, and integrity were evaluated by comet assay, using PrestoBlueTM reagent and lactate dehydrogenase (LDH) leakage test. The data obtained indicate that both native and particulate polyphenols added immediately after UV-C exposure increased cell viability in a dose-dependent manner; however, the efficiency of particulate quercetin was more pronounced than that of the native compound; also quercetin coated with a (CH/DexS)4 shell more effectively than the native compound reduced the number of DNA lesions in the nuclei of keratinocytes exposed to UV-C radiation; native and particulate resveratrol were ineffective against DNA damage. Quercetin reduces cell death caused by UV-C radiation and increases DNA repair capacity. Coating quercetin with (CH/DexS)4 shell markedly enhanced its impact on DNA repair.

DNA Repair Activation and Cell Death Suppression by Plant Polyphenols in Keratinocytes Exposed to Ultraviolet Irradiation.

This work investigated effects of plant polyphenolic compounds (PPs) on responses of cultured human HaCaT keratinocytes to ultraviolet radiation in the C range (UV-C). The experimental data obtained indicate a cytoprotective effect of PPs added immediately after UV-C exposure. The efficiency of PPs was lowered in the following order: acacetin ≥ silybin > quercetin. The influence of PPs on phosphorylation of histone H2AX and the number of single-strand DNA breaks in the nuclei of keratinocytes were also studied. Using the comet assay and γH2AX staining, followed by fluorescence microscopy, it has been established that PPs can reduce DNA damage in the nuclei of keratinocytes exposed to UV-C. It is concluded that PPs can diminish the destructive effect of UV radiation on skin cells, activating the process of repairing genetic damage.

Effects of pre- and post-treatment with plant polyphenols on human keratinocyte responses to solar UV.

BACKGROUND: The understanding of the anti-inflammatory mechanisms of action of plant polyphenols (PPs) and clarification of the relationship between their anti-inflammatory and antioxidant properties may result in a new therapeutic approach to skin cancers. OBJECTIVE: To elucidate the underlying mechanism, we analyzed the ability of PPs to attenuate inflammatory, metabolic and oxidative cellular responses to UV irradiation. METHODS: Normal human epidermal keratinocytes (NHEK) were exposed to physiologically relevant dose of solar-simulated UV irradiation. Effects of pre- and post-treatment with PPs on the overproduction of peroxides and inflammatory mediators (mRNA and protein) were analyzed using real-time RT-PCR, enzyme-linked immunosorbent and fluorometric techniques. RESULTS: Differences between the effectiveness of pre- and post-treatment with polyphenols was found. In particular, PPs post-treatment, but not pretreatment, completely abolished overexpression of Cyp1a1 and Cyp1b1 genes and elevation of intracellular peroxides in NHEK irradiated by UV. Post-treatment with PPs also more efficiently than pretreatment prevented UV-induced overexpression of IL-1 beta, IL-6 and COX2 mRNAs. CONCLUSION: Our data strongly suggest that PPs predominantly affect delayed molecular and cellular events initiated in NHEK by solar UV rather than primary photochemical reactions. PPs may be important component in cosmetic formulations for post-sun skin care.