Miyoung Park

Carnosic acid, a phenolic diterpene from rosemary, prevents UV-induced expression of matrix metalloproteinases in human skin fibroblasts and keratinocytes

Exposure of the skin to ultraviolet (UV) irradiation induces photoageing through the up‐regulation of matrix metalloproteinases (MMPs) and subsequent breakdown of extracellular matrices. Reactive oxygen species (ROS) and epidermal growth factor receptor (EGFR) activation play central roles in UV‐induced MMP expression through initiating extracellular signal‐regulated kinase (ERK)–mediated AP‐1 signalling. We aimed to explore the effects of carnosic acid (CA), a phenolic diterpene from rosemary, on UV‐induced MMP expression in human skin cells. Molecular mechanism underlying the effects of CA was also examined in the aspect of MMP expression, ERK/AP‐1 pathway, ROS generation and EGFR activation. Human dermal fibroblast cell line (Hs68), primary normal human dermal fibroblasts (HDFs) and normal human epidermal keratinocytes (HEKs) were employed, and antiphotoageing effects of CA were assessed by Western blotting, quantitative real‐time PCR and enzyme assays. CA significantly inhibited UVA‐ and UVB‐induced expression of MMP‐1, MMP‐3 and MMP‐9 in a concentration‐dependent manner in Hs68 cells. UVB‐induced ERK activation and the formation of transcription factor, AP‐1, were significantly suppressed by CA. Among the upstream events of MMP expression, UVB‐induced ROS generation was attenuated by CA, while EGFR activation was not affected. Confirming the antiphotoageing effects of CA through the suppression of UV‐induced ROS generation, UVB‐enhanced GADD45 expression, a marker for oxidative DNA damages was significantly reduced by CA. Inhibitory effects of CA on UVB‐induced MMP expression could be also seen in HDFs and HEKs. Collectively, our study demonstrates that CA inhibits the UV‐enhanced MMPs in human skin cells through the inhibition of ROS and the suppression of ERK/AP‐1 activation.

Liver X Receptor Activation Inhibits Melanogenesis through the Acceleration of ERK-Mediated MITF Degradation

Liver X receptors (LXRs) are nuclear receptors that act as ligand-activated transcription factors regulating lipid metabolism and inflammation. In the skin, activation of LXRs stimulates differentiation of keratinocytes and augments lipid synthesis in sebocytes. However, the function of LXRs in melanocytes remains largely unknown. We investigated whether LXR activation would affect melanogenesis. In human primary melanocytes, MNT-1, and B16 melanoma cells, TO901317, a synthetic LXR ligand, inhibited melanogenesis. Small interfering RNA (siRNA) experiments revealed the dominant role of LXRβ in TO901317-mediated antimelanogenesis. Enzymatic activities of tyrosinase were unaffected, but the expression of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2 was suppressed by TO901317. Expressions of microphthalmia-associated transcription factor (MITF), a master transcriptional regulator of melanogenesis, and cAMP-responsive element-binding activation were not affected. It is noteworthy that the degradation of MITF was accelerated by TO901317. Extracellular signal-regulated kinase (ERK) contributed to TO901317-induced antimelanogenesis, which was evidenced by recovery of melanogenesis with ERK inhibitor. Other LXR ligands, 22(R)-hydroxycholesterol (22(R)HC) and GW3965, also activated ERK and suppressed melanogenesis. The intermediary role of Ras was confirmed in TO901317-induced ERK phosphorylation. Finally, antimelanogenic effects of TO901317 were confirmed in vivo in UVB-tanning model in brown guinea pigs, providing a previously unreported line of evidence that LXRs may be important targets for antimelanogenesis.

A novel adamantyl benzylbenzamide derivative, AP736, suppresses melanogenesis through the inhibition of cAMP-PKA-CREB-activated microphthalmia-associated transcription factor and tyrosinase expression

Melanogenesis is essential for the protection of skin against UV, but excessive production of melanin causes unaesthetic hyperpigmentation. Much effort is being made to develop effective depigmenting agents. Here, we found that a tyrosinase inhibitor, AP736 (5‐adamantan‐1‐yl‐N‐(2,4‐dihydroxy‐benzyl)‐2,4‐dimethoxy‐benzamide) potently suppresses tyrosinase expression, and the mechanism underlying was elucidated. AP736 attenuated the melanin production induced by diverse melanogenic stimuli in murine and human melanocytes. It suppressed the expression of key melanogenic enzymes; tyrosinase, tyrosinase‐related protein‐1 and tyrosinase‐related protein‐2. The expression of microphthalmia‐associated transcription factor (MiTF), a major promoter of melanogenesis was also decreased. AP736 inhibited the activation of cAMP response element‐binding protein (CREB) and phosphokinase A (PKA), and cAMP elevation, reflecting that cAMP‐PKA‐CREB signalling axis was suppressed, resulting in the downregulation of MiTF and tyrosinase. Along with the previously reported tyrosinase inhibitory activity, the suppression of cAMP‐PKA‐CREB‐mediated MiTF and tyrosinase expression by AP736 may be efficient for the treatment for hyperpigmentation.

Different effects of five depigmentary compounds, rhododendrol, raspberry ketone, monobenzone, rucinol and AP736 on melanogenesis and viability of human epidermal melanocytes

Numerous medications are used to treat hyperpigmentation. However, several reports have indicated that repeated application of some agents, such as rhododendrol (RD), raspberry ketone (RK) and monobenzone (MB), can be toxic to melanocytes. Although these agents had severe side effects in human trials, no current in vitro methods can predict the safety of such drugs. This study assessed the in vitro effects of five depigmentary compounds including leukoderma‐inducing agents. In particular, we determined the effects of different concentrations and exposure times of different depigmentary agents on cell viability and melanogenesis in the presence and absence of ultraviolet B (UVB) radiation. Concentrations of RD, RK and MB that inhibit melanogenesis are similar to concentrations that are cytotoxic; however, concentrations of rucinol (RC) and AP736 that inhibit melanogenesis are much lower than concentrations that are cytotoxic. Furthermore, the concentrations that cause toxic effects depend on exposure duration, and prolonged exposure to RD, RK and MB had more cytotoxic effects than prolonged exposure to RC and AP736. The cytotoxic effects of RD and RK appear to be mediated by apoptosis due to increased expression of caspase‐3 and caspase‐8; UVB radiation increased the cytotoxicity of these agents and also increased caspase activity. Our results indicate that different leukoderma‐inducing compounds have different effects on the viability of normal epidermal melanocytes and suggest that the in vitro assay used here can be used to predict whether an investigational compound that induces leukoderma may lead to adverse effects in human trials.

Compound K inhibits MMP-1 expression through suppression of c-Src-dependent ERK activation in TNF-α-stimulated dermal fibroblast.

Compound K (CK) is one of the major metabolites of ginsenosides exhibiting a variety of pharmacological properties such as anti‐ageing, anti‐oxidation and anti‐inflammatory activities. However, the protective efficacy of CK in abnormal skin conditions with inflammatory responses was not examined. Here, we investigated the effects of CK on matrix metalloproteinase‐1 (MMP‐1) and type I procollagen production in tumor necrosis factor‐α (TNF‐α)‐stimulated human skin fibroblasts HS68 cells and human skin equivalents. We found that CK suppressed MMP‐1 secretion and increased the level of reduced type I procollagen secretion, caused by the inhibition of extracellular signal‐regulated kinase (ERK) activation, but not p38 and c‐Jun N‐terminal kinase (JNK) activation in TNF‐α‐stimulated HS68 cells. Then, we focused on the involvement of the c‐Src and epidermal growth factor receptor (EGFR) as upstream signalling molecules for ERK activation by TNF‐α in HS68 cells. CK suppressed the phosphorylation of c‐Src/EGFR by TNF‐α, which led to the inactivation of downstream signalling molecules including AKT and MEK. In addition, CK suppressed AP‐1 (c‐jun and c‐fos) phosphorylation as downstream transcription factors of active ERK for MMP‐1 expression in TNFα‐stimulated HS68 cells. These results showed novel mechanisms by which CK inhibits TNF‐α‐induced MMP‐1 expression through the inactivation of c‐Src/EGFR‐dependent ERK/AP‐1 signalling pathway, resulting in the inhibition of collagen degradation in human fibroblast cells. Therefore, CK may be a promising protective agent for the treatment of inflammatory skin conditions such as skin ageing and atopic dermatitis.

Evaluation of Eye Irritation Potential of Solid Substance with New 3D Reconstructed Human Cornea Model, MCTT HCE(TM).

The eye irritation potential of drug candidates or pharmaceutical ingredients should be evaluated if there is a possibility of ocular exposure. Traditionally, the ocular irritation has been evaluated by the rabbit Draize test. However, rabbit eyes are more sensitive to irritants than human eyes, therefore substantial level of false positives are unavoidable. To resolve this species difference, several three-dimensional human corneal epithelial (HCE) models have been developed as alternative eye irritation test methods. Recently, we introduced a new HCE model, MCTT HCETM which is reconstructed with non-transformed human corneal cells from limbal tissues. Here, we examined if MCTT HCETM can be employed to evaluate eye irritation potential of solid substances. Through optimization of washing method and exposure time, treatment time was established as 10 min and washing procedure was set up as 4 times of washing with 10 mL of PBS and shaking in 30 mL of PBS in a beaker. With the established eye irritation test protocol, 11 solid substances (5 non-irritants, 6 irritants) were evaluated which demonstrated an excellent predictive capacity (100% accuracy, 100% specificity and 100% sensitivity). We also compared the performance of our test method with rabbit Draize test results and in vitro cytotoxicity test with 2D human corneal epithelial cell lines.

18β-glycyrrhetinic acid attenuates anandamide-induced adiposity and high-fat diet induced obesity.

SCOPE Previous reports suggest that licorice extract has various metabolically beneficial effects and may help to alleviate adiposity and hyperlipidemia. However, underlying anti-obesity mechanisms still remain elusive. Moreover, it is unknown which single ingredient in licorice extract would mediate such effects. We aimed to demonstrate that licorice extract and its active ingredients can inhibit adipocyte differentiation and fat accumulation. METHODS AND RESULTS 18β-glycyrrhetinic acid (18β-GA) alleviated the effects of CB1R agonist, anandamide (AEA) on CB1R signaling in a concentration-dependent manner. Consistently, 18β-GA suppressed AEA-induced adipocyte differentiation in 3T3-L1 cells through the downregulation of AEA-induced MAPK activation and expression of adipogenic genes including C/EBP-α and PPAR-γ. The protein levels of fatty acid synthase and stearoyl-CoA desaturase 1 were also decreased and the phosphorylation of acetyl-CoA carboxylase was increased in 18β-GA pretreated cells. The supplementation of 18β-GA significantly lowered body weight, fat weight, and plasma lipids levels in obese animal models. CONCLUSION These results may provide a novel insight into the molecular mechanism involved in anti-adipogenic and anti-obesity effects of 18β-GA by suppressing the activation of CB1R induced by AEA. Thus, 18β-GA may exert beneficial effects against obesity-related metabolic disorders.

Real-time monitoring of adipocyte differentiation using a capacitance sensor array.

As obesity and its associated metabolic diseases become a worldwide epidemic, the demand for novel anti-obesity agents is increasing. We report a label-free and real-time monitoring method that uses a capacitance sensor array to screen anti-obesity agents. The results for the real-time capacitance of 3T3-L1 cells treated with 12 different chemicals extracted from natural products were consistent with the biochemical indicators of adipogenesis such as the expression of perilipin, the major protein coating the surface of lipid droplets in adipocytes. The data demonstrate that a capacitance change during adipocyte differentiation is closely associated with lipid accumulation in the cells, suggesting that adipocyte differentiation can be monitored in real time. This capacitance sensor might be used for label-free and real-time monitoring of adipocyte differentiation, and may facilitate the development of high throughput screening methods for anti-obesity drugs.

Performance standard-based validation study for local lymph node assay: 5-bromo-2-deoxyuridine-flow cytometry method

Local lymph node assay: 5-bromo-2-deoxyuridine-flow cytometry method (LLNA: BrdU-FCM) is a modified non-radioisotopic technique with the additional advantages of accommodating multiple endpoints with the introduction of FCM, and refinement and reduction of animal use by using a sophisticated prescreening scheme. Reliability and accuracy of the LLNA: BrdU-FCM was determined according to OECD Test Guideline (TG) No. 429 (Skin Sensitization: Local Lymph Node Assay) performance standards (PS), with the participation of four laboratories. Transferability was demonstrated through successfully producing stimulation index (SI) values for 25% hexyl cinnamic aldehyde (HCA) consistently greater than 3, a predetermined threshold, by all participating laboratories. Within- and between-laboratory reproducibility was shown using HCA and 2,4-dinitrochlorobenzene, in which EC2.7 values (the estimated concentrations eliciting an SI of 2.7, the threshold for LLNA: BrdU-FCM) fell consistently within the acceptance ranges, 0.025-0.1% and 5-20%, respectively. Predictive capacity was tested using the final protocol version 1.3 for the 18 reference chemicals listed in OECD TG 429, of which results showed 84.6% sensitivity, 100% specificity, and 88.9% accuracy compared with the original LLNA. The data presented are considered to meet the performance criteria for the PS, and its predictive capacity was also sufficiently validated.

Synthesis and structure-activity relationship of cyclopentenone oximes as novel inhibitors of the production of tumor necrosis factor-α.

3-Alkyl-2-aryl-2-cyclopenten-1-one oxime derivatives (1) were studied as a novel class of inhibitors of tumor necrosis factor α (TNF-α) with regard to synthesis and in vitro SAR inhibition of TNF-α. The in vitro IC50 values of these compounds in rat and human peripheral blood mononuclear cells were at the sub-micromolar level.