Differentiation-dependent expression of NADP(H):quinone oxidoreductase-1 via NF-E2 related factor-2 activation in human epidermal keratinocytes

BackgroundNADP(H):quinone oxidoreductase-1 (NQO-1) is known for its protective role in skin carcinogenesis, but the expression of NQO-1 during keratinocyte (KC) differentiation has not been studied.ObjectiveThe purpose of the current study was to evaluate modulation of NQO-1 and NF-E2-related factor-2 (Nrf2) during KC differentiation.MethodsNormal human epidermal keratinocytes (NHEKs) were induced to differentiation by prolonged culture after confluency (postconfluence).ResultsNQO-1 was induced at the late stage of differentiation of NHEKs (7th day of postconfluence). The expression of postconfluence-induced NQO-1 was stimulated by 0.1 mM H2O2, but attenuated by 5 mM N-acetylcysteine, implying that reactive oxygen species (ROS) are implicated in the expression of NQO-1 in differentiated KCs. Nrf2 was up-regulated at the earlier than NQO-1 induction (3rd day of postconfluence). The Nrf2-dependent expression of NQO-1 was further supported by Nrf2-siRNA experiments. A confocal study confirmed the differentiation-dependent induction and activation of NOQ-1 and Nrf-2 in NHEKs. Immunohistochemistry showed that NQO-1 was accentuated in the upper epidermal layers, supporting the notion that differentiation-dependent NQO-1 expression is functional in human skin in vivo.ConclusionThese results demonstrate that NQO-1 is modulated during KC differentiation via Nrf2 pathway, suggesting the active role of NQO-1 in the differentiating epidermis.