Hakwon Kim

The behavior of quartz crystal microbalance in high pressure CO2

Abstract Quartz crystal microbalance (QCM) is a very useful in situ tool for measuring minute changes of mass of thin surface films with real-time monitoring. The effect of temperature deviation and pressure change, viscosity and roughness loading on the frequency shift were examined by measuring the frequency change of bare QCM under high-pressure CO 2 . From a contour analysis, the frequency shift from viscosity loading and that from roughness loading were obtained. Frequency shift from viscosity loading was about three to four times larger than that estimated by Kanazawas equation. The resonator, whose surface roughness was larger than the diffusion length, exhibited a frequency shift from roughness loading.

Suppression of thymus- and activation-regulated chemokine (TARC/CCL17) production by 3-O-β-D-glucopyanosylspinasterol via blocking NF-κB and STAT1 signaling pathways in TNF-α and IFN-γ-induced HaCaT keratinocytes.

A phytosterol derivative, 3-O-β-D-glucopyanosylspinasterol (spinasterol-Glc) isolated from leaves of Stewartia koreana was reported to inhibit LPS-induced cytokine production in macrophage cells. Thymus and activation regulated chemokine (TARC/CCL17) is produced in response to pro-inflammatory cytokines in keratinocytes, which is implicated in the development of inflammatory skin diseases. In present study, we investigated the effect of spinasterol-Glc on production of TARC/CCL17 induced by TNF-α and IFN-γ in human HaCaT keratinocytes. Spinasterol-Glc inhibited the mRNA and protein expression of TARC/CCL17 induced by TNF-α/IFN-γ in a dose-dependent manner. Inhibitors of c-Raf-1, p38 MAPK, and JAK2, suppressed the TNF-α/IFN-γ-induced production of TARC/CCL17, and phosphorylation of these signaling molecules were attenuated by spinasterol-Glc. The compound also inhibited phosphorylation of IKKα/β and IκB-α, and reduced translocation of NF-κB to the nucleus. We demonstrated that spinasterol-Glc suppressed the NF-κB-driven and the GAS-driven expression of luciferase reporter gene induced by TNF-α and IFN-γ. In addition, spinasterol-Glc inhibited the DNA binding of NF-κB and STAT1 to its cognate binding site. These results suggest that spinasterol-Glc has effective inhibitory effects on production of TARC/CCL17 in keratinocytes via inhibition of NF-κB as well as STAT activation, and could be utilized for development of a potential therapeutic agent against skin inflammatory diseases.

Inhibitory effect of 5,6-dihydroergosteol-glucoside on atopic dermatitis-like skin lesions via suppression of NF-κB and STAT activation.

BACKGROUND Atopic dermatitis (AD) is a Th2-type disease. Keratinocytes, a major type in the skin, produce Th2 chemokines such as thymus and activation-regulated chemokine (TARC)/CCL17 and macrophage-derived chemokine (MDC)/CCL22, which play pivotal roles in the development of Th2-dominant inflammatory skin diseases. Recently, it was reported that 5,6-dihydroergosterol-glucoside (DHE-Glc) was synthesized and exhibited strong anti-inflammatory activity. OBJECTIVE We aimed to investigate the effects of DHE-Glc, a synthetic molecule derived from ergosterol, on AD-like skin lesions induced by 2,4-dinitrochlorobenzene (DNCB) in mice and to elucidate the effects of DHE-Glc on TNF-α/IFN-γ-induced production of CCL17 and CCL22 in human keratinocytes (HaCaTs) and DNCB induced skin inflammation mice model. METHOD Mice were sensitized and challenged on the skin of their backs with DNCB. At 30-60 days after sensitization, mice were treated with cutaneous administration of DHE-Glc by skin smear. HaCaT cells were used to evaluate the effects of DHE-Glc on production of CCL17 and CCL22 and investigate mechanisms of action by RT-PCR, ELISA, Western blot, and reporter assays. RESULT Topical administration of DHE-Glc attenuated AD-like skin inflammatory symptoms. DHE-Glc decreased infiltration of epidermal eosinophils and mast cells, and reduced levels of IgE, histamine, and mRNA expression and protein levels of CCL17/CCL22 in the plasma of DNCB-treated animals. In addition, DHE-Glc suppressed TNF-α/IFN-γ-induced expression of the Th2 chemokines CCL17 and CCL22 by inhibiting NF-κB and STAT activation in TNF-α/IFN-γ-induced HaCaT cells. CONCLUSION DHE-Glc improved AD-like skin inflammatory symptoms on the backs of DNCB-induced mice, partly by suppressing production of Th2 chemokines, CCL17 and CCL22 in inflamed skin. Therefore, DHE-Glc is a potential therapeutic agent for skin inflammatory diseases such as AD.

Gomisin N Inhibits Melanogenesis through Regulating the PI3K/Akt and MAPK/ERK Signaling Pathways in Melanocytes.

Gomisin N, one of the lignan compounds found in Schisandra chinensis has been shown to possess anti-oxidative, anti-tumorigenic, and anti-inflammatory activities in various studies. Here we report, for the first time, the anti-melenogenic efficacy of Gomisin N in mammalian cells as well as in zebrafish embryos. Gomisin N significantly reduced the melanin content without cellular toxicity. Although it was not capable of modulating the catalytic activity of mushroom tyrosinase in vitro, Gomisin N downregulated the expression levels of key proteins that function in melanogenesis. Gomisin N downregulated melanocortin 1 receptor (MC1R), adenylyl cyclase 2, microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2 (TRP-2). In addition, Gomisin N-treated Melan-A cells exhibited increased p-Akt and p-ERK levels, which implies that the activation of the PI3K/Akt and MAPK/ERK pathways may function to inhibit melanogenesis. We also validated that Gomisin N reduced melanin production by repressing the expression of MITF, tyrosinase, TRP-1, and TRP-2 in mouse and human cells as well as in developing zebrafish embryos. Collectively, we conclude that Gomisin N inhibits melanin synthesis by repressing the expression of MITF and melanogenic enzymes, probably through modulating the PI3K/Akt and MAPK/ERK pathways.

YH18968, a Novel 1,2,4-Triazolone G-Protein Coupled Receptor 119 Agonist for the Treatment of Type 2 Diabetes Mellitus

G protein-coupled receptor 119 (GPR119) is expressed in the pancreas and gastrointestinal tract, and its activation promotes insulin secretion in the beta cells of the pancreatic islets as well as the secretion of glucagon-like peptide-1 (GLP-1) in intestinal L cells, consequently improving glucose-stimulated insulin secretion. Due to this dual mechanism of action, the development of small-molecule GPR119 agonists has received significant interest for the treatment of type 2 diabetes. We newly synthesized 1,2,4-triazolone derivatives of GPR119 agonists, which demonstrated excellent outcomes in a cyclic adenosine monophosphate (cAMP) assay. Among the synthesized derivatives, YH18968 showed cAMP=2.8 nM; in GLUTag cell, GLP-1secretion=2.3 fold; in the HIT-T15 cell, and insulin secretion=1.9 fold. Single oral administration of YH18968 improved glucose tolerance and combined treatment with a dipeptidyl peptidase 4 (DPP-4) inhibitor augmented the glucose lowering effect as well as the plasma level of active GLP-1 in normal mice. Single oral administration of YH18968 improved glucose tolerance in a diet induced obese mice model. This effect was maintained after repeated dosing for 4 weeks. The results indicate that YH18968 combined with a DPP-4 inhibitor may be an effective therapeutic candidate for the treatment of type 2 diabetes.