Sae Woong Oh

Cannabidiol upregulates melanogenesis through CB1 dependent pathway by activating p38 MAPK and p42/44 MAPK

Melanogenesis plays a critical role in the protection of skin against external stresses such as ultraviolet irradiation and oxidative stressors. This study was aimed to investigate the effects of cannabidiol on melanogenesis and its mechanisms of action in human epidermal melanocytes. We found that cannabidiol increased both melanin content and tyrosinase activity. The mRNA levels of microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein (TRP) 1, and TRP2 were increased following cannabidiol treatment. Likewise, cannabidiol increased the protein levels of MITF, TRP 1, TRP 2, and tyrosinase. Mechanistically, we found that cannabidiol regulated melanogenesis by upregulating MITF through phosphorylation of p38 mitogen-activated protein kinase (MAPK) and p42/44 MAPK, independent of cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling. In addition, the melanogenic effect of cannabidiol was found to be mediated by cannabinoid CB1 receptor, not by CB2 receptor. Taken together, these findings indicate that cannabidiol-induced melanogenesis is cannabinoid CB1 receptor-dependent, and cannabidiol induces melanogenesis through increasing MITF gene expression which is mediated by activation of p38 MAPK and p42/44 MAPK. Our results suggest that cannabidiol might be useful as a protective agent against external stresses.

Vanillin attenuates negative effects of ultraviolet A on the stemness of human adipose tissue-derived mesenchymal stem cells.

Ultraviolet A (UVA) irradiation induces various changes in cell biology. The objective of this study was to determine the effect of vanillin on UVA irradiation-induced damages in the stemness properties of human adipose tissue-derived mesenchymal stem cells (hAMSCs). UVA-antagonizing mechanisms of vanillin were also examined. The results revealed that vanillin attenuated UVA-induced reduction of the proliferative potential and stemness of hAMSCs evidenced by increased proliferative activity in BrdU incorporation assay and upregulation of stemness-related genes (OCT4, NANOG and SOX2) in response to vanillin treatment. UVA-induced reduction in mRNA level of hypoxia-inducible factor (HIF)-1α was significantly recovered by vanillin. In addition, the antagonizing effect of vanillin on UVA was found to be mediated by reduced production of PGE2 through inhibiting JNK and p38 MAPK. Taken together, these findings showed that vanillin could improve the reduced stemness of hAMSCs induced by UVA. The effect of vanillin is mediated by upregulating HIF-1α via inhibiting PGE2-cAMP signaling. Therefore, vanillin might be used as an antagonizing agent to mitigate the effects of UVA.

Afzelin positively regulates melanogenesis through the p38 MAPK pathway

Melanogenesis refers to synthesis of the skin pigment melanin, which plays a critical role in the protection of skin against ultraviolet irradiation and oxidative stressors. We investigated the effects of afzelin on melanogenesis and its mechanisms of action in human epidermal melanocytes. In this study, we found that afzelin increased both melanin content and tyrosinase activity in a concentration-dependent manner. While the mRNA levels of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein (TRP)-1 increased following afzelin treatment, the mRNA levels of TRP-2 were not affected by afzelin. Likewise, afzelin increased the protein levels of MITF, TRP-1, and tyrosinase but not TRP-2. Mechanistically, we found that afzelin regulated melanogenesis by upregulating MITF through phosphorylation of p38 mitogen-activated protein kinase (MAPK), independent of cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling. Taken together, these findings indicate that the promotion of melanogenesis by afzelin occurs through increased MITF gene expression, which is mediated by activation of p38 MAPK, and suggest that afzelin may be useful as a protective agent against ultraviolet irradiation.

Globular adiponectin acts as a melanogenic signal in human epidermal melanocytes

Adiponectin is an adipocyte‐derived cytokine that circulates as a full‐length protein and a fragment containing the globular domain of adiponectin (gAd). A recent study has reported the antimelanogenic effects of full‐length adiponectin.

Anti-melanogenic effects of resorcinol are mediated by suppression of cAMP signaling and activation of p38 MAPK signaling

Abstract In this study, we investigated the inhibitory mechanisms of resorcinol in B16F10 mouse melanoma cells. We found that resorcinol reduced both the melanin content and tyrosinase activity in these cells. In addition, resorcinol suppressed the expression of melanogenic gene microphthalmia-associated transcriptional factor (MITF) and its downstream target genes tyrosinase, tyrosinase-related protein (TRP)-1, and TRP-2. In addition, we found that resorcinol reduced intracellular cAMP levels and protein kinase A (PKA) activity, and increased phosphorylation of the p38 mitogen-activated protein kinase (MAPK). Resorcinol was also found to directly inhibit tyrosinase activity. However, resorcinol-induced decrease in melanin content, tyrosinase activity, and tyrosinase protein levels were attenuated by SB203580, a p38 MAPK inhibitor. Taken together, these data indicate that anti-melanogenic activity of resorcinol is be mediated through the inhibition of cAMP signaling and activation of p38 MAPK, indicating that resorcinol may be a possible ameliorating agent in the treatment of hyperpigmentation skin disorders. Schematic diagram of resorcinol function in melanogenesis.

Beauvericin inhibits melanogenesis by regulating cAMP/PKA/CREB and LXR-α/p38 MAPK-mediated pathways.

Melanogenesis is the process of production of melanin pigments that are responsible for the colors of skin, eye, and hair and provide protection from ultraviolet radiation. However, excessive levels of melanin formation cause hyperpigmentation disorders such as freckles, melasma, and age spots. Liver X receptors (LXR) are nuclear oxysterol receptors belonging to the family of ligand-activated transcription factors and physiological regulators of lipid and cholesterol metabolism. In the skin, activation of LXRs stimulates differentiation of keratinocytes and augments lipid synthesis in sebocytes. However, the function of LXRs in melanogenesis has not been clearly elucidated. In addition, although beauvericin, a well-known mycotoxin primarily isolated from several fungi, has various biological properties, its involvement in melanogenesis has not been reported. Therefore, in this study, we examined the effects of beauvericin on melanogenesis and its molecular mechanisms. Beauvericin decreased melanin content and tyrosinase activity without any cytotoxicity. Beauvericin also reduced protein levels of MITF, tyrosinase, TRP1, and TRP2. In addition, beauvericin suppressed cAMP-PKA-CREB signaling and upregulated expression of LXR-α, resulting in the suppression of p38 MAPK. Our results indicate that beauvericin attenuates melanogenesis by regulating both cAMP/PKA/CREB and LXR-α/p38 MAPK pathways, consequently leading to a reduction of melanin levels.

Arctigenin protects against ultraviolet-A-induced damage to stemness through inhibition of the NF-κB/MAPK pathway

The stemness of stem cells is negatively affected by ultraviolet A (UVA) irradiation. This study was performed to examine the effects of arctigenin on UVA-irradiation-induced damage to the stemness of human mesenchymal stem cells (hMSCs) derived from adipose tissue. The mechanisms of action of arctigenin were also investigated. A BrdU-incorporation assay demonstrated that arctigenin attenuated the UVA-induced reduction of the cellular proliferative potential. Arctigenin also increased the UVA-induced reduction in stemness of hMSCs by upregulating stemness-related genes such as SOX2, OCT4, and NANOG. In addition, the UVA-induced reduction in the mRNA expression level of hypoxia-inducible factor (HIF)-1α was significantly recovered by arctigenin. The antagonizing effect of arctigenin on UVA irradiation was mediated by reduced PGE2 production through the inhibition of MAPKs (p42/44 MAPK, p38 MAPK, and JNK) and NF-κB. Overall, these findings suggest that arctigenin can ameliorate the reduced stemness of hMSCs induced by UVA irradiation. The effects of arctigenin are mediated by PGE2-cAMP signaling-dependent upregulation of HIF-1α. Therefore, arctigenin could be used as an antagonist to attenuate the effects of UVA irradiation.

Zingerone protects keratinocyte stem cells from UVB-induced damage

The epidermis, the outermost layer of the skin, is a stratified epithelium that protects the body from the external environment. Keratinocyte stem cells (KSCs) are involved in epidermis homeostasis by maintaining epidermal integrity through a process of constant regeneration. Ultraviolet B (UVB) radiation is a major inducer of cellular damage in the epidermis. In this study, we investigated the effects of zingerone (a phenolic compound derived from spices) on UVB-induced cellular damage in KSCs. We found that zingerone significantly inhibited cellular senescence of KSCs in response to UVB irradiation. These effects were confirmed by the senescence-associated β-galactosidase and comet assays. Zingerone decreased the production of proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in UVB-irradiated KSCs. Moreover, UVB-induced expression of p21, a cell cycle arrest-related gene, was reduced by zingerone treatment, whereas zingerone upregulated the expression of proliferation-related genes such as proliferating cell nuclear antigen (PCNA) and vascular endothelial growth factor (VEGF), in addition to anti-senescence-related genes including telomerase reverse transcriptase (TERT), histone deacetylase 1 (HDAC1), and DNA (cytosine-5)-methyltransferase 1 (DNMT1). The UVB-protective effects of zingerone were mediated by inhibition of p42/44 MAPK and p38 MAPK. Therefore, zingerone could potentially be used to protect the epidermis from UVB-induced damage.

Stemness and differentiation potential-recovery effects of sinapic acid against ultraviolet-A-induced damage through the regulation of p38 MAPK and NF-κB

Ultraviolet A (UVA) irradiation exerts negative effects on stemness and differentiation potential of stem cells. This study aimed to explore the effect of sinapic acid on UVA-irradiation-induced damages to stemness and differentiation potential of human-adipose-tissue-derived mesenchymal stem cells (hAMSCs) and its UVA-antagonist mechanisms. Sinapic acid attenuated UVA-induced reduction in the proliferative potential and stemness by upregulating OCT4, SOX2, and NANOG. In addition, sinapic acid significantly recovered UVA-induced reduction in expression level of hypoxia-inducible factor (HIF)-1α. The antagonist effect of sinapic acid against stemness damage was mediated by reduceing PGE2 production through inhibition of p38 MAPK and NF-κB. Moreover, sinapic acid attenuated UVA-induced reduction in differentiation potential by downregulating the expression of macrophage migration inhibitory factor (MIF) and Kruppel-like factor (KLF) 2 gene while activating AMP-activated protein kinase (AMPK). UVA-induced inhibition of adipogenic differentiation was mediated by reducing MIF production through suppression of NF-κB. Taken together, these findings suggest that sinapic acid may ameliorate UVA-irradiation-induced reduced stemness and differentiation potential of hAMSCs. Therefore, sinapic acid might have potential as an antagonist agent to attenuate damages caused by UVA.

Melanogenic mechanism of ethanolic extract of Dalbergia odorifera

Vitiligo and hair graying are acquired chronic hypopigmentary disorders of the skin. This study was carried out to investigate the effect of ethanolic extract of D. odorifera (DOE) on melanogenesis and determine its mechanism of action in B16F10 mouse melanoma cells and human epidermal melanocytes. DOE increased melanin content levels. It also enhanced the expression of microphthalmia-associated transcription factor (MITF) gene and its downstream target genes tyrosinase-related protein (TRP) 1, TRP 2, and tyrosinase. DOE increased cAMP levels, as determined by a cAMP production assay. In addition, DOE increased PKA activity and induced phosphorylation of cAMP response element binding (CRE B) protein, its downstream signaling protein. However, DOE showed no effects on mitogen-activated kinases (MAPKs) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Taken together, DOE induces melanogenesis by upregulating MITF gene through the cAMPCREB signaling pathway, which suggests its potential for the treatment of hypopigmentary skin diseases.