Hyun Ju Kwon

Phlorotannins isolated from the edible brown alga Ecklonia stolonifera exert anti-adipogenic activity on 3T3-L1 adipocytes by downregulating C/EBPα and PPARγ

The dramatic increase in obesity-related diseases emphasizes the need to elucidate the cellular and molecular mechanisms underlying fat metabolism. Inhibition of adipocyte differentiation has been suggested to be an important strategy for preventing or treating obesity. In our previous study, we characterized an Ecklonia stolonifera extract and non-polar fractions thereof, including dichloromethane and ethyl acetate fractions. We showed that these fractions inhibited adipocyte differentiation and lipid formation/accumulation in 3T3-L1 preadipocytes, as assessed by Oil Red O staining. As part of our ongoing search for anti-obesity agents derived from E. stolonifera, in this work, we characterized five known phlorotannins, including phloroglucinol, eckol, dieckol, dioxinodehydroeckol, and phlorofucofuroeckol A, all of which were isolated from the active ethyl acetate fraction of E. stolonifera. We determined the chemical structures of these phlorotannins through comparisons of published nuclear magnetic resonance (NMR) spectral data. Furthermore, we screened these phlorotannins for their abilities to inhibit adipogenesis over a range of concentrations (12.5-100 μM). Of these five phlorotannins, phloroglucinol, eckol, and phlorofucofuroeckol A significantly concentration-dependently inhibited lipid accumulation in 3T3-L1 cells without affecting cell viability. In addition, the five isolated phlorotannins also significantly reduced the expression levels of several adipocyte marker genes, including proliferator activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα), although they did so to different extents. These results suggest that the molecular weight of a phlorotannin is an important factor affecting its ability to inhibit adipocyte differentiation and modulate the expression levels of adipocyte marker genes.

Widdrol induces cell cycle arrest, associated with MCM down-regulation, in human colon adenocarcinoma cells

Widdrol, an odorous compound extracted from Juniperus chinensis, has been shown to inhibit the in vitro growth of in human cancer cells. This study was conducted on cultured human colon adenocarcinoma HT29 cells to elucidate the possible mechanisms by which widdrol exerts its anti-proliferative activity, which until now has remained poorly understood. It was found that widdrol induces accumulation of sub-G1 phase and arrests in the G1 phase of the cell cycle. Induction of G1 arrest by widdrol was correlated with induction of Chk2, p53 phosphorylation and CDK inhibitor p21 expression as well as inhibition of cyclin E, cyclin-dependent kinase (CDK2) and retinoblastoma protein (pRB). Moreover, mini-chromosome maintenance (MCM) proteins were markedly down-regulated in HT29 cells treated with widdrol. Altogether, these results show widdrol possesses potential anti-cancer activity against colon adenocarcinoma cells by inhibiting their proliferation and inducing cell cycle G1 arrest.

Induction of apoptosis by esculetin in human leukemia U937 cells: roles of Bcl-2 and extracellular-regulated kinase signaling.

In the present study, we reported that apoptosis induced by esculetin, a phenolic compound with apoptotic activity in cancer cells, was markedly blocked by Bcl-2-overexpression, but restored by HA14-1, a small-molecule Bcl-2 inhibitor, in human leukemic U937 cells. The combined use of esculetin and HA14-1 effectively induced Bid cleavage and loss of mitochondrial membrane potential (MMP, Deltapsi(m)) leading to the activation of caspases and cleavage of poly(ADP-ribose) polymerase (PARP) in Bcl-2-overexpressing (U937/Bcl-2) cells. Combined treatment with esculetin and HA14-1 upregulated the expression of death receptor 4 (DR4), and activation of extracellular-regulated kinase (ERK) in a time-dependent manner. In addition, esculetin and HA14-1-mediated apoptosis was reduced by ERK inhibitors through inhibition of DR4 expression, suggesting that the synergistic effect was at least partially mediated through ERK-dependent induction of DR4 expression. The results indicate that HA14-1-induced reversal of the anti-apoptotic effect of Bcl-2 confers apoptosis sensitivity to esculetin by a mitochondrial amplification step and through the ERK-dependent induction of DR4 expression in U937/Bcl-2 cells. Thus, HA14-1 reversal of Bcl-2-mediated esculetin resistance suggests a novel strategy for increasing esculetin sensitivity in Bcl-2-overexpressing leukemia cells.

Widdrol induces apoptosis via activation of AMP-activated protein kinase in colon cancer cells

Widdrol, a natural sesquiterpene present in Juniperus sp., has been shown to exert anticancer and antifungal effects. Emerging evidence has suggested that AMP-activated protein kinase (AMPK), which functions as a cellular energy sensor, is a potential therapeutic target for human cancers. In this study, we found that AMPK mediates the anticancer effects of widdrol through induction of apoptosis in HT-29 colon cancer cells. We showed that widdrol induced the phosphorylation of AMPK in a dose- and time-dependent manner. The selective AMPK inhibitor compound C abrogated the inhibitory effect of widdrol on HT-29 cell growth. In addition, we demonstrated that widdrol induced apoptosis and this was associated with the activation of caspases, including caspase‑3/7 and caspase-9, in HT-29 cells. We also demonstrated that transfection of HT-29 cells with AMPK siRNAs significantly suppressed the widdrol-mediated apoptosis and the activation of caspases. However, cell cycle arrest induced by widdrol was not affected by transfection of HT-29 cells with AMPK siRNAs. Furthermore, widdrol inhibited HT-29 tumor growth in a human tumor xenograft model. Taken together, our results suggest that the anticancer effect of widdrol may be mediated, at least in part, by induction of apoptosis via AMPK activation.

Betulinic acid isolated from Vitis amurensis root inhibits 3-isobutyl-1-methylxanthine induced melanogenesis via the regulation of MEK/ERK and PI3K/Akt pathways in B16F10 cells.

Previously, betulinic acid was identified as one of the main compounds responsible for the anti-melanogenic effect in Vitis amurensis root. In this study, we investigated the precise mechanism underlying the anti-melanogenic activity of betulinic acid in B16F10 cells. Betulinic acid significantly attenuated 3-isobutyl-1-methylxanthine (IBMX)-induced melanin production by inhibiting tyrosinase, tyrosinase related protein (TRP)-1, and TRP-2 expression through the modulation of their corresponding transcription factors, microphthalamia associated transcription factor (MITF) and cAMP response element binding protein (CREB), in B16F10 cells. In addition, phosphorylation of mitogen-activated protein kinase kinase (MEK)/extracellular regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Akt, involved in the melanogenic processes, were ameliorated by betulinic acid treatment. Role of MEK/ERK and PI3K/Akt signaling pathway in the melanogenesis was confirmed by using specific inhibitors, PD98059 (for MEK/ERK) and LY294002 (for PI3K/Akt), respectively. As a result, betulinic acid inhibited melanin production by tyrosinase, TRP-1, and TRP-2 inhibition through the regulation of CREB and MITF, which was accompanied with MEK/ERK and PI3K/Akt inactivation in IBMX-stimulated B16F10 cells. Consequently, these results demonstrate a novel molecular function of betulinic acid derived from V. amurensis root in melanogenesis, which in turn enhances our understanding on the application of cosmetic therapy for reducing skin hyperpigmentation.

Antiadipogenic Effect of Vitis amurensis Root Methanol Extract and Its Solvent Fractions in 3T3-L1 Preadipocytes

왕머루(Vitis amurensis Rupreche)는 아시아 지역에서 자생하는 포도의 한 종류로서 항산화, 항염증, 뇌신경보호, 신생혈관 억제능 등의 생리활성이 알려져 있다. 왕머루의 뿌리는 한국에서 전통적인 약재로 사용되어왔으나 그 생리활성에 대해서는 보고된 바가 적다. 이에 본 연구에서는 머루근 MeOH 추출물(VARM)과 그 용매 분획물이 지방세포분화 및 지방 생성에 미치는 영향을 3T3-L1 preadipocyte를 이용하여 분석하였다. 그 결과 VARM은 3T3-L1 preadipocyte의 지방 세포로의 분화, 지방 축적, 중성 지방 생성량을 독성 없이 농도의존적으로 유의적으로 억제시켰다. 활성 물질의 규명을 위해 VARM으로부터 dichloromethane (

Inhibition of Adipocyte Differentiation by Methanol Extracts of Oenanthe javanica Seed in 3T3-L1 Preadipocytes

CH_2Cl_2

Anti-cancer Activity of Osmanthus matsumuranus Extract by Inducing G2/M Arrest and Apoptosis in Human Hepatocellular Carcinoma Hep G2 Cells

), ethyl acetate (EtOAc), n-butanol (n-BuOH), 그리고 물(

Antiobesity Activity of Chrysanthemum zawadskii Methanol Extract

H_2O

Curcumin Blocks Naproxen-Induced Gastric Antral Ulcerations through Inhibition of Lipid Peroxidation and Activation of Enzymatic Scavengers in Rats.

) 층의 순서로 용매 분획을 실시한 후 지방 생성에 미치는 영향을 분석한 결과