UVB protective effects of Sargassum horneri through the regulation of Nrf2 mediated antioxidant mechanism.

The present study aimed to evaluate the protective effect of a methanol extract of Sargassum horneri (SHM), which contains 6-hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydrobenzofuran-2(4H)-one (HTT) and apo-9'-fucoxanthinone, against ultraviolet B (UVB)-induced cellular damage in human keratinocytes and its underlying mechanism. SHM significantly improved cell viability of UVB-exposed human keratinocytes by reducing the generation of intracellular reactive oxygen species (ROS). Moreover, SHM inhibited UVB exposure-induced apoptosis by reducing the formation of apoptotic bodies and the populations of the sub-G1 hypodiploid cells and the early apoptotic cells by modulating the expression of the anti- and pro-apoptotic molecules, Bcl-2 and Bax, respectively. Furthermore, SHM inhibited NF-κB p65 activation by inducing the activation of Nrf2/HO-1 signaling. The cytoprotective and antiapoptotic activities of SHM are abolished by the inhibition of HO-1 signaling. In further study, SHM restored the skin dryness and skin barrier disruption in UVB-exposed human keratinocytes. Based to these results, our study suggests that SHM protects the cells against UVB-induced cellular damages through the Nrf2/HO-1/NF-κB p65 signaling pathway and may be potentially useful for the prevention of UVB-induced skin damage.

Downregulation of pro-inflammatory mediators by a water extract of Schisandra chinensis (Turcz.) Baill fruit in lipopolysaccharide-stimulated RAW 264.7 macrophage cells.

Schisandra chinensis has a long-standing history of medicinal use as a tonic, a sedative, an anti-tussive, and an anti-aging drug. Nevertheless, the antagonistic effects of S. chinensis against lipopolysaccharide (LPS)-stimulated responses have not yet been studied. In this study, we investigated whether water extract of S. chinensis fruit (WESC) has the ability to attenuate the expression of pro-inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PGE2), and tumor necrosis factor-α (TNF-α) in LPS-stimulated RAW 264.7 macrophage cells. WESC inhibited the expression of LPS-induced pro-inflammatory mediators, namely, NO, PGE2, and TNF-α. Furthermore, gene expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α was inhibited both at mRNA and protein synthesis levels, without any cytotoxic effect. Moreover, WESC significantly suppressed LPS-induced DNA-binding activity of NF-κB by inhibiting degradation of IκBα. It was found that pyrrolidine dithiocarbamate (PDTC), a specific NF-κB inhibitor, downregulates the expression of these pro-inflammatory genes to be closely regulated by NF-κB activity. Furthermore, we found that WESC retains dephosphorylation of Akt in response to LPS, and consequently suppressed the DNA-binding activity of NF-κB in RAW 264.7 macrophage cells. LY294002, a specific Akt inhibitor, attenuated LPS-induced pro-inflammatory gene expression via suppression of NF-κB activity. Taken together, our results indicate that WESC downregulates the expression of pro-inflammatory genes involved in the synthesis of NO, PGE2, and TNF-α in LPS-stimulated RAW 264.7 macrophage cells by suppressing Akt-dependent NF-κB activity.