Sauchinone, a Lignan from <i>Saururus chinensis</i>, Protects Human Skin Keratinocytes against Ultraviolet B-Induced Photoaging by Regulating the Oxidative Defense System

Abstract

Ultraviolet (UV) radiation from sunlight induces matrix metalloproteinase (MMP) expression, which are responsible for collagenous extracellular matrix proteins breakdown in skin, causing photoaging. Sauchinone is reported to have various bioactivity such as antioxidative, hepatoprotective, and anti-inflammatory effects. In the present study, we investigated the protective effect of sauchinone against UVB (50 mJ/cm 2 )-induced photoaging in HaCaT human epidermal keratinocytes. Sauchinone, at 5-40 µm, significantly protected keratinocytes against UVB-induced damage as assessed by cell viability and toxicity assay. Additionally, sauchinone, at 20-40 µm, prevented the upregulation of MMP-1 proteins and reduction of type 1 collagen induced by UVB. Other assays revealed that, in keratinocytes, sauchinone decreased reactive oxygen species (ROS) production and increased glutathione levels and heme oxygenase-1. Sauchinone also inhibited UVB-induced phosphorylation of mitogen-activated protein kinase (MAPK) signaling pathways. These results demonstrated that sauchinone protects skin keratinocytes through inhibition of extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAPK signaling via upregulation of oxidative defense enzymes.Key words sauchinone; matrix metalloproteinase-1; antiphotoaging; antioxidative; type 1 collagen; ultraviolet B Skin aging can be attributed to intrinsic and extrinsic aging (photoaging).1) Damage to skin due to passage of time (intrinsic aging) and to repeated exposures to ultraviolet (UV) radiation (photoaging) are considered distinct entities. 1) UV radiation, particularly UVB (290-320 nm) from sunlight, leads to direct DNA damage, reactive oxygen species (ROS) formation, and the associated to the extracellular matrix structural integrity.2) UVB-irradiation induces the over-expression of various proteins that are involved in cellular damage responses and signaling-transduction pathways.2,3) Particularly, the expression of UVB-induced matrix metalloproteinase-1 (MMP-1), the interstitial collagenase, leads to the breakdown of collagen and is thus related to photoaging.4) The most abundant structural protein in skin connective tissue is type 1 collagen (COL1A1), which is responsible for conferring resiliency and strength. 4,5) Primarily, skin aging is related to reduction in COL1A1 levels, which is the principal component of skin. 5)

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