Dermato-protective properties of ergothioneine through induction of Nrf2/ARE-mediated antioxidant genes in UVA-irradiated Human keratinocytes.

UVA irradiation-induced skin damage and redox imbalance have been shown to be ameliorated by ergothioneine (EGT), a naturally occurring sulfur-containing amino acid. However, the responsible molecular mechanism with nanomolar concentrations of EGT remains unclear. We investigated the dermato protective efficacies of EGT (125-500nM) against UVA irradiation (15J/cm(2)), and elucidated the underlying molecular mechanism in human keratinocyte-derived HaCaT cells. We found that EGT treatment prior to UVA exposure significantly increased the cell viability and prevented lactate dehydrogenase release into the medium. UVA-induced ROS and comet-like DNA formation were remarkably suppressed by EGT with a parallel inhibition of apoptosis, as evidenced by reduced DNA fragmentation (TUNEL), caspase-9/-3 activation, and Bcl-2/Bax dysregulation. Furthermore, EGT alleviated UVA-induced mitochondrial dysfunction. Dose-dependent increases of antioxidant genes, HO-1, NQO-1, and γ-GCLC and glutathione by EGT were associated with upregulated Nrf2 and downregulated Keap-1 expressions. This was confirmed by increased nuclear accumulation of Nrf2 and inhibition of Nrf2 degradation. Notably, augmented luciferase activity of ARE may explain Nrf2/ARE-mediated signaling pathways behind EGT dermato-protective properties. We further demonstrated that Nrf2 translocation was mediated by PI3K/AKT, PKC, or ROS signaling cascades. This phenomenon was confirmed with suppressed nuclear Nrf2 activation, and consequently diminished antioxidant genes in cells treated with respective pharmacological inhibitors (LY294002, GF109203X, and N-acetylcysteine). Besides, increased basal ROS by EGT appears to be crucial for triggering the Nrf2/ARE signaling pathways. Silencing of Nrf2 or OCTN1 (EGT carrier protein) signaling with siRNA showed no such protective effects of EGT against UVA-induced cell death, ROS, and apoptosis, which is evidence of the vitality of Nrf2 translocation and protective efficacy of EGT in keratinocytes. Our findings conclude that EGT at nanomolar concentrations effectively ameliorated UVA-induced skin damage, and may be considered as a desirable food supplement for skin protection and/or preparation of skin care products.

Lucidone protects human skin keratinocytes against free radical-induced oxidative damage and inflammation through the up-regulation of HO-1/Nrf2 antioxidant genes and down-regulation of NF-κB signaling pathway.

We investigated the protective effects of lucidone, a naturally occurring cyclopentenedione isolated from the fruits of Lindera erythrocarpa Makino, against free-radical and inflammation stimulator 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress in human keratinocyte (HaCaT) cells, with the aim of revealing the possible mechanisms underlying the protective efficacy. Lucidone pretreatment (0.5-10 µg/mL) markedly increased HaCaT cell viability and suppressed AAPH-induced reactive oxygen species (ROS) generation, lipid peroxidation, and DNA damage. Notably, the antioxidant potential of lucidone was directly correlated with the increased expression of an antioxidant gene, heme oxygenase 1 (HO-1), which was followed by the augmentation of the nuclear translocation and transcriptional activation of NF-E2-related factor-2 (Nrf2), with or without AAPH. Nrf2 knockdown diminished the protective effects of lucidone. We also observed that lucidone pretreatment inhibited AAPH-induced inflammatory chemokine prostaglandin E2 (PGE2) production and the expression of cyclooxygenase-2 (COX-2) in HaCaT cells. Lucidone treatment also significantly inhibited AAPH-induced nuclear factor-κB (NF-κB) activation and suppressing the degradation of inhibitor-κB (I-κB). Furthermore, lucidone significantly diminished AAPH-induced COX-2 expression through the down-regulation of the extracellular signal-regulated kinase (ERK) and p38 MAPK signaling pathways. Therefore, lucidone may possess antioxidant and anti-inflammatory properties and may be useful for the prevention of free radical-induced skin damage.