Cynanoside F Controls Skin Inflammation by Suppressing Mitogen-Activated Protein Kinase Activation.

Atopic dermatitis (AD) is a chronic inflammatory skin disease accompanied by severe itching and dry skin. Currently, the incidence of AD due to excessive activation of immune cells by various environmental factors is increasing worldwide, and research on inflammatory response inhibitors with fewer side effects is continuously needed. Cynanoside F (CF) is one of the pregnane-type compounds in the root of Cynanchum atratum, an oriental medicinal herb that has been shown to have antioxidant, antitumor, and anti-inflammatory effects. Although CF has been isolated as a component in Cynanchum atratum, the scientific role of CF has not yet been explored. In this study, we evaluated the effect of CF on AD and revealed the mechanism using in vitro and in vivo experimental models. CF significantly reduced lipopolysaccharide (LPS)-induced protein expression levels of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and cyclooxygenase-2 (COX-2), which are important proinflammatory mediators in the RAW264.7 macrophage cell line. CF did not inhibit the nuclear factor-kappa B (NF-κB) signaling activated by LPS but significantly reduced the phosphorylation of mitogen-activated protein kinases (MAPKs), such as p38 MAPK, JNK, and ERK. CF consistently inhibited the activity of the activator protein-1 (AP-1) transcription factor, a downstream molecule of MAPK signaling. In addition, in an experiment using an oxazolone-induced AD mouse model, the CF-treated group showed a marked decrease in epidermal thickness, the number of infiltrated mast cells, and the amount of histamine. The mRNA levels of IL-1ß, interleukin-4 (IL-4), and thymic stromal lymphopoietin (TSLP) were consistently lowered in the group treated with CF. Moreover, the phosphorylation of c-Jun and c-Fos protein levels, which are the AP-1 components, were lowered in the skin tissues of CF-treated mice. These results provide the first evidence that CF has an inhibitory effect on AD and suggest the possibility of CF being developed as a potential therapeutic agent for AD.

Cynanchi atrati and Its Phenolic Constituent Sinapic Acid Target Regulator of Calcineurin 1 (RCAN1) to Control Skin Inflammation.

Atopic dermatitis (AD) is a common inflammatory skin disorder, and numerous pharmacological approaches are employed to reduce symptoms. Natural products of plant-derived materials have been accepted as complementary therapy for the treatment of a wide range of inflammatory diseases. Cynanchi atrati (CA) is an oriental medicinal herb used in the treatment of acute urinary infection, febrile diseases, and laryngopharyngitis. However, the role of CA root extract in skin inflammation such as AD has not been explored yet. In this study, we examined the possible effect of CA root extract on skin inflammation and evaluated the underlying signaling mechanism using in vitro and in vivo modeling systems. Raw264.7 macrophages were used for in vitro experiments, and an oxazolone-induced AD mouse model was used to evaluate in vivo effects. CA extract significantly inhibited the expression levels of lipopolysaccharide (LPS)-induced pro-inflammatory cytokines such as interleukin-6 (IL-6) and interleukin-1ß (IL-1ß) in RAW264.7 macrophages. The CA root extract mediated suppression of pro-inflammatory cytokine expression and was associated with the decreased nuclear factor kappa B (NF-κB) gene transcriptional activation. Moreover, CA root extract attenuated the in vivo expression of IL-6 and tumor necrosis factor-α (TNF-α) and ear swelling in the AD mouse models. We also observed that the inhibitory effect of CA root extract on skin inflammation was accompanied by the upregulation of calcineurin 1 (RCAN1) expression, which functions in the inflammatory pathways by suppressing NF-κB signaling. We consistently observed that the immunosuppressive effect of CA root extract in AD was significantly perturbed in the RCAN1 knockout mice. In addition, we isolated a phenolic acid compound, sinapic acid (SA), from the CA root extract and found that SA consistently exerted an immunosuppressive effect in RAW264.7 macrophages by inducing RCAN1 expression. Our results provide the first evidence that CA root extract and its phenolic acid constituent, SA, modulate NF-κB signaling pathways by inducing RCAN1 expression in the skin inflammation process. Thus, we suggest that CA root extract has a therapeutic value for the treatment of AD by targeting endogenous immune regulators.

Trichosanthes kirilowii extract enhances repair of UVB radiation­induced DNA damage by regulating BMAL1 and miR­142­3p in human keratinocytes.

Ultraviolet B (UVB) radiation induces DNA damage, oxidative stress and inflammation, and suppresses the immune system in the skin, which collectively contribute to skin aging and carcinogenesis. The DNA damage response, including DNA repair, can be regulated by the circadian clock and microRNA (miRNA) expression. The aim of the present study was to evaluate the reparative action of Trichosanthes kirilowii extract (TKE) against UVB irradiation­induced DNA damage in human keratinocytes. TKE demonstrated low cytotoxicity in normal HaCaT keratinocytes at low doses (up to 100 µg/ml). The results of a comet assay revealed that TKE enhanced the repair of UVB­induced DNA damage. TKE significantly upregulated the expression of the core clock protein, brain and muscle aryl hydrocarbon receptor nuclear translocator­like protein­1 (BMAL1), and downregulated the expression of miRNA (miR)­142­3p, as demonstrated using western blotting and the reverse transcription­quantitative polymerase chain reaction. Furthermore, the suppression of miR­142­3p by a specific inhibitor positively correlated with the repair activity. Overall, the data obtained demonstrated that TKE enhanced the repair of UVB­induced DNA damage by regulating the expression of BMAL1 and miR­142­3p. Consequently, TKE can be considered a potential candidate for the treatment of skin diseases associated with UVB­induced damage.