Protopanaxatriol (PPT) is a secondary intestinal metabolite of ginsenoside in ginseng. Although the effects of PPT have been reported in various diseases including cancer, diabetes and inflammatory diseases, the skin protective effects of PPT are poorly understood. HaCaT cells were treated with PPT in a dose-dependent manner. mRNA and protein levels which related to skin barrier and hydration were detected compared with retinol. Luciferase assay was performed to explore the relative signaling pathway. Western blot was conducted to confirm these pathways and excavated further signals. PPT enhanced the expression of filaggrin (FLG), transglutaminase (TGM)-1, claudin, occludin and hyaluronic acid synthase (HAS) −1, −2 and −3. The mRNA expression levels of FLG, TGM-1, HAS-1 and HAS-2 were suppressed under NF-κB inhibition. PPT significantly augmented NF-κB-luc activity and upregulated Src/AKT/NF-κB signaling. In addition, PPT also increased phosphorylation of the mitogen-activated protein kinases (MAPKs) ERK, JNK and p38 and upstream MAPK activators (MEK and MKK). Furthermore, transcriptional activity of AP-1 and CREB, which are downstream signaling targets of MAPK, was enhanced by PPT. PPT improves skin barrier function and hydration through Src/AKT/NF-κB and MAPK signaling. Therefore, PPT may be a valuable component for cosmetics or treating skin disorders.

Chloranthalactone B (CTB), a lindenane-type sesquiterpenoid, was obtained from the Chinese medicinal herb Sarcandra glabra, which is frequently used as a remedy for inflammatory diseases. However, the anti-inflammatory mechanisms of CTB have not been fully elucidated. In this study, we investigated the molecular mechanisms underlying these effects in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. CTB strongly inhibited the production of nitric oxide and pro-inflammatory mediators such as prostaglandin E₂, tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and IL-6 in RAW264.7 cells stimulated with LPS. A reverse-transcription polymerase chain reaction assay and Western blot further confirmed that CTB inhibited the expression of inducible nitric oxide synthase, cyclooxygenase-2, TNF-α, and IL-1β at the transcriptional level, and decreased the luciferase activities of activator protein (AP)-1 reporter promoters. These data suggest that inhibition occurred at the transcriptional level. In addition, CTB blocked the activation of p38 mitogen-activated protein kinase (MAPK) but not c-Jun N-terminal kinase or extracellular signal-regulated kinase 1/2. Furthermore, CTB suppressed the phosphorylation of MKK3/6 by targeting the binding sites via formation of hydrogen bonds. Our findings clearly show that CTB inhibits the production of inflammatory mediators by inhibiting the AP-1 and p38 MAPK pathways. Therefore, CTB could potentially be used as an anti-inflammatory agent.

For the first time, a pale amorphous coumarin derivative, 5-methoxyl aesculetin (MOA), was isolated from the dried bark of Fraxinus rhynchophylla Hance (Oleaceae). MOA modulates cytokine expression in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages, but the precise mechanisms are still not fully understood. We determined the effects of MOA on the production of inflammatory mediators and pro-inflammatory cytokines in the LPS-induced inflammatory responses of RAW 264.7 macrophages. MOA significantly inhibited the LPS-induced production of nitric oxide (NO), prostaglandin E₂ (PGE₂), tumor necrosis factor-α (TNF-α), interleukin-6, and interleukin-1β. It also effectively attenuated inducible nitric oxide (NO) synthase, cyclooxygenase-2, and TNF-α mRNA expression and significantly decreased the levels of intracellular reactive oxygen species. It inhibited phosphorylation of the extracellular signal-regulated kinase (ERK1/2), thus blocking nuclear translocation of activation protein (AP)-1. In a molecular docking study, MOA was shown to target the binding site of ERK via the formation of three hydrogen bonds with two residues of the kinase, which is sufficient for the inhibition of ERK. These results suggest that the anti-inflammatory effects of MOA in RAW 264.7 macrophages derive from its ability to block both the activation of mitogen-activated protein kinases (MAPKs) and one of their downstream transcription factors, activator protein-1 (AP-1). Our observations support the need for further research into MOA as a promising therapeutic agent in inflammatory diseases.